RHYTHMS NET CONNECTIONS INC
424B4, 1999-04-07
TELEPHONE COMMUNICATIONS (NO RADIOTELEPHONE)
Previous: EBAY INC, PRE 14A, 1999-04-07
Next: EL PASO ENERGY CORP/DE, S-4, 1999-04-07



<PAGE>
P_R_O_S_P_E_C_T_U_S
 
                                9,375,000 SHARES
 
                                     [LOGO]
 
                          RHYTHMS NETCONNECTIONS INC.
 
                                  COMMON STOCK
 
                                 --------------
 
    This is Rhythms' initial public offering of common stock. The common stock
will trade on The Nasdaq National Market under the symbol "RTHM".
 
    INVESTING IN THE COMMON STOCK INVOLVES RISKS WHICH ARE DESCRIBED IN THE
"RISK FACTORS" SECTION BEGINNING ON PAGE 8 OF THIS PROSPECTUS.
 
                               -----------------
 
<TABLE>
<CAPTION>
                                                                PER SHARE       TOTAL
                                                               -----------  --------------
<S>                                                            <C>          <C>
Public Offering Price........................................       $21.00    $196,875,000
Underwriting Discount........................................     $1.39125     $13,042,969
Proceeds, before expenses, to Rhythms........................    $19.60875    $183,832,031
</TABLE>
 
    The underwriters may also purchase up to an additional 1,406,250 shares at
the public offering price, less the underwriting discount, within 30 days from
the date of this prospectus to cover over-allotments.
 
    Neither the Securities and Exchange Commission nor any state securities
commission has approved or disapproved of these securities or determined if this
prospectus is truthful or complete. Any representation to the contrary is a
criminal offense.
 
    The shares of common stock will be ready for delivery in New York, New York
on or about April 12, 1999.
 
                               ------------------
 
                          JOINT BOOK-RUNNING MANAGERS
 
MERRILL LYNCH & CO.                                         SALOMON SMITH BARNEY
 
                                  -----------
 
HAMBRECHT & QUIST                                     THOMAS WEISEL PARTNERS LLC
 
                                  -----------
 
                 The date of this prospectus is April 6, 1999.
<PAGE>
            [MAP OF UNITED STATES SHOWING RHYTHMS NATIONAL COVERAGE]
 
    Our goal is to provide service in 50 metropolitan areas which contain
approximately 60% of U.S. LANs.*
 
    *In addition to the 33 metropolitan areas indicated above, our plan is to
launch service in an additional 17 metropolitan areas in 2000.
 
          [MAP OF UNITED STATES SHOWING RHYTHMS NETWORK ARCHITECTURE]
 
                                       2
<PAGE>
                               TABLE OF CONTENTS
 
<TABLE>
<CAPTION>
                                                                                                               PAGE
                                                                                                             ---------
<S>                                                                                                          <C>
Summary....................................................................................................          4
Risk Factors...............................................................................................          8
Use of Proceeds............................................................................................         22
Dividend Policy............................................................................................         22
Capitalization.............................................................................................         23
Dilution...................................................................................................         24
Selected Consolidated Financial Data.......................................................................         25
Management's Discussion and Analysis of Financial Condition and Results of Operations......................         26
Description of Certain Indebtedness........................................................................         32
Business...................................................................................................         33
Management.................................................................................................         53
Certain Relationships and Related Transactions.............................................................         64
Principal Stockholders.....................................................................................         68
Description of Capital Stock...............................................................................         70
Shares Eligible for Future Sale............................................................................         74
Underwriting...............................................................................................         75
Legal Matters..............................................................................................         77
Experts....................................................................................................         77
Where You Can Find More Information........................................................................         77
Glossary of Terms..........................................................................................        A-1
Index to Financial Statements..............................................................................        F-1
</TABLE>
 
    WE HAVE NOT AUTHORIZED ANY DEALER, SALESPERSON OR OTHER PERSON TO GIVE ANY
INFORMATION OR TO MAKE ANY REPRESENTATIONS OTHER THAN THOSE CONTAINED IN THIS
PROSPECTUS. IF THEY GIVE YOU SUCH INFORMATION OR MAKE SUCH REPRESENTATIONS, YOU
MUST NOT RELY UPON THEM AS HAVING BEEN AUTHORIZED BY US OR THE UNDERWRITERS.
THIS PROSPECTUS IS NOT AN OFFER TO SELL, OR THE SOLICITATION OF AN OFFER TO BUY,
ANY SECURITIES OTHER THAN THESE REGISTERED SECURITIES. IT IS ALSO NOT AN OFFER
TO, OR SOLICITATION OF, ANY PERSON IN ANY JURISDICTION IN WHICH SUCH OFFER OR
SOLICITATION WOULD BE UNLAWFUL. NEITHER THE DELIVERY OF THIS PROSPECTUS NOR ANY
OFFER OR SALE SHALL, UNDER ANY CIRCUMSTANCES, CREATE ANY IMPLICATION THAT WE
HAVE HAD NO CHANGE IN OUR BUSINESS SINCE THE DATE OF THIS PROSPECTUS OR THAT THE
INFORMATION CONTAINED IN THIS PROSPECTUS IS CORRECT AS OF ANYTIME AFTER THE DATE
OF THIS PROSPECTUS.
 
    We use market data and industry forecasts throughout this prospectus, which
we have obtained from internal surveys, market research, publicly available
information and industry publications. Industry publications generally state
that the information they provide has been obtained from sources believed to be
reliable, but that the accuracy and completeness of such information is not
guaranteed. Similarly, we believe that the surveys and market research we or
others have performed is reliable, but we have not independently verified this
information. Neither we nor any of the underwriters represents that any such
information is accurate.
 
    We own applications for federal registration and claim rights in the
following trademarks: ACI-TM-; ACCELERATED CONNECTIONS-TM-; APPLINET-TM-; CHOICE
ROUTE-TM-; DSL ... CAN YOU HANDLE THE SPEED?-TM-; HOME.RHYTHMS-TM-;
LOOP.RHYTHMS-TM-; NET.RHYTHMS-TM-; NETRHYTHMS-TM-; RHYTHM WORKS-TM-;
RHYTHMS-TM-; RHYTHMS COGNITIVE NETWORK-TM-; RHYTHMS NETCONNECTIONS-TM-; RHYTHMS
PBXPRESS-TM-; RHYTHMS TOOLBAR-TM-; RING.RHYTHMS-TM-; WORK.RHYTHMS-TM- and
[LOGO].
 
    This prospectus also refers to trade names and trademarks of other
companies.
 
                                       3
<PAGE>
                                    SUMMARY
 
    THIS SUMMARY HIGHLIGHTS CERTAIN SIGNIFICANT ASPECTS OF OUR BUSINESS AND THIS
OFFERING, BUT YOU SHOULD READ THE ENTIRE PROSPECTUS, INCLUDING THE FINANCIAL
DATA AND RELATED NOTES, BEFORE MAKING AN INVESTMENT DECISION. WHEN WE REFER TO
OUR COMPANY IN THIS PROSPECTUS, WE REFER TO US AND OUR SUBSIDIARIES, AS A
COMBINED ENTITY, EXCEPT WHERE WE INDICATE OTHERWISE. UNLESS OTHERWISE NOTED, ALL
COMMON STOCK NUMBERS IN THIS PROSPECTUS GIVE RETROACTIVE EFFECT TO A TWO FOR ONE
STOCK SPLIT EFFECTED IN NOVEMBER 1998 AND A SIX FOR FIVE STOCK SPLIT EFFECTED IN
MARCH 1999 AND ASSUME THE CONVERSION OF ALL OUTSTANDING SHARES OF PREFERRED
STOCK INTO COMMON STOCK UPON COMPLETION OF THIS OFFERING AND THAT THE
UNDERWRITERS WILL NOT EXERCISE THEIR OVER-ALLOTMENT OPTION. WE HAVE PROVIDED A
GLOSSARY OF TERMS FOR YOUR CONVENIENCE BEGINNING ON PAGE A-1. YOU SHOULD
CAREFULLY CONSIDER THE INFORMATION SET FORTH UNDER "RISK FACTORS."
 
    We are a leading service provider of high-speed local access networking
solutions using digital subscriber line ("DSL") technology to businesses. We
have designed our network to give our customers a high-speed "always on" local
connection to the Internet and to private local and wide area networks. We offer
a variety of DSL technologies that deliver data transfer rates ranging from 128
Kilobits per second (Kbps) to 7.1 Megabits per second (Mbps). For customers that
subscribe at the 7.1 Mbps rate, our network provides transfer speeds faster than
frame relay and T-1 circuits, and is approximately 125 times the speed of the
fastest dial-up modem and over 55 times the speed of integrated services digital
network (ISDN) lines. Through our packet-based network, multiple users on a
single connection are able to simultaneously access the Internet and private
networks. Beyond high-speed access, we also offer a growing suite of features
and applications that we can individually configure to each user's needs. We
believe our network solutions will increase remote office and worker
productivity and reduce the complexity of communications for businesses.
 
    Since our inception in February 1997, we have made substantial progress in
implementing a scalable nationwide network. We began offering commercial
services in San Diego in April 1998, and have subsequently begun service in ten
additional markets: San Francisco, San Jose, Oakland/East Bay, Chicago, Los
Angeles, Orange County, Boston, Sacramento, New York and Philadelphia. We intend
to continue our network rollout into an additional 23 markets in 1999 and a
further 17 markets by the end of 2000. Upon completion of this network
expansion, we anticipate providing services in 50 of the nation's largest
metropolitan areas, which we believe contain 60% of the nation's local area
networks. We have signed interconnection agreements with Ameritech, Bell
Atlantic, BellSouth, GTE, Pacific Bell and U S WEST, and we are currently
pursuing interconnection arrangements with two other incumbent carriers. As of
January 31, 1999, we provide service or have installed equipment in nearly 200
incumbent carrier central offices. We have obtained competitive carrier
authority or have been permitted to operate as a competitive carrier in 21
states.
 
    In March 1999, we entered into separate strategic arrangements with MCI
WorldCom, Inc. and Microsoft Corporation. As part of our strategic arrangements,
MCI WorldCom's investment fund and Microsoft each invested $30 million in us.
The MCI WorldCom arrangement also designates us as MCI WorldCom's preferred
provider of business DSL lines in certain circumstances, and provides that MCI
WorldCom is committed to sell at least 100,000 of our DSL lines over a period of
five years, subject to penalties for failure to reach target commitments. In
turn, we have designated MCI WorldCom as our preferred provider of network
services in certain circumstances. MCI WorldCom will also work with us to
develop voice and data applications over a single DSL connection. In our
Microsoft arrangement, we will jointly distribute with Microsoft a co-branded
DSL version of the Microsoft Network (MSN) service focused on our small business
customers and on our customers' teleworkers. In April 1999, we entered into a
customer relationship with Qwest Communications Corporation, in connection with
which Qwest's wholly owned subsidiary, U.S. Telesource, Inc., invested $15
million in us.
 
    We also market our services through our direct sales force and through our
partnerships with recognized leaders in the networking industry, including
Microsoft and Cisco Systems, Inc. Under our
 
                                       4
<PAGE>
strategic partnership with Cisco, Cisco agreed to jointly market and sell our
networking solutions to its customer base and will engage in joint development
projects with us. As of January 31, 1999, we had over 650 lines in service, and
we are currently under contract to supply over 9,000 additional DSL lines to our
business and service provider customers, including Cisco, Silicon Graphics,
Inc., QUALCOMM Incorporated, Wind River Systems and Broadcom Corporation.
 
    Our senior management team has extensive experience in developing
next-generation networking businesses. Our President and Chief Executive
Officer, Catherine Hapka, was previously the founder, President and Chief
Operating Officer of !NTERPRISE Networking Services, U S WEST's data networking
business. Scott Chandler, our Chief Financial Officer, was previously President
and Chief Executive Officer of C-COR Electronics, Inc., a manufacturer of
broadband telecommunications equipment. James Greenberg, our Chief Network
Officer, directed the design, planning, operation and construction of Sprint
Corporation's data networks. Frank Tolve, our Chief Sales Officer, previously
served as Vice President, Sales Operations of Bay Networks. Our sponsors, which
include Microsoft, MCI WorldCom's investment fund, Qwest's subsidiary, Kleiner
Perkins Caufield & Byers, Enterprise Partners, Brentwood Venture Capital, the
Sprout Group and a subsidiary of Enron Corp., have to date invested
approximately $105.3 million.
 
MARKET OPPORTUNITY
 
    We believe that a substantial market opportunity exists as a result of the
convergence of six factors:
 
    - the growing demand for high-speed access to the Internet and corporate
      networks;
 
    - the inherent limitations of dial-up modems as a connection to data
      networks;
 
    - the need for large companies to improve the productivity of their remote
      offices and workers;
 
    - the need for small and medium businesses to have an integrated
      communication solution for their networking requirements;
 
    - the increasing adoption of DSL and widespread use of packet-based
      networks; and
 
    - the 1996 Telecommunications Act.
 
    These factors create a dual market opportunity: new carriers can create
efficient high-speed data, voice and video networks using existing
infrastructure, and business customers can better address their local and wide
area networking needs through a single carrier.
 
THE RHYTHMS SOLUTIONS
 
    We believe our network solutions effectively address many of the unmet
communication needs of today's businesses by offering an appealing combination
of quality, performance, price and service. Our network consists of:
 
    - HIGH-SPEED, "ALWAYS ON" LOCAL CONNECTIONS. Using DSL technology over
      standard telephone lines, our network is capable of delivering data at
      speeds ranging from 128 Kbps to 7.1 Mbps.
 
    - METROPOLITAN AND WIDE AREA OVERLAY NETWORK. We have designed our network
      architecture so that we can effectively and efficiently manage data
      traffic within and among metropolitan areas in which we offer our
      services. We manage the network and monitor service levels on a nationwide
      basis from our Network Operations Center in Denver.
 
    - PRODUCTIVITY-ENHANCING FEATURES AND APPLICATIONS. We offer a growing suite
      of network-enabled features and applications to extend the functionality
      of corporate communications and networking resources for remote offices
      and workers. We also offer high performance Internet
 
                                       5
<PAGE>
      access solutions to remote offices and workers as well as small and medium
      businesses in conjunction with our Internet Service Provider customers.
 
    - SERVICE FLEXIBILITY. We have designed our network so that, over a single
      DSL connection, we are able to customize the features and applications for
      each individual user and local area network user.
 
    - TURNKEY SOLUTION. We offer turnkey network solutions for our customers by
      providing each customer with a single point of contact for all of our
      services, including network implementation, maintenance and billing.
 
BUSINESS STRATEGY
 
    Our goal is to become the leading national service provider of high
performance networking solutions for remote offices and workers. We intend to
implement the following strategies in an effort to achieve our goal:
 
    - exploit our early market entrance by deploying our network rapidly and
      building strong relationships with businesses and service provider
      customers;
 
    - focus on businesses that demand high performance networking solutions;
 
    - use our network as a platform for productivity-enhancing features and
      applications that we and third parties develop;
 
    - continue to establish strong distribution channels to reach large, medium
      and small businesses; and
 
    - provide superior service and customer care.
 
                            ------------------------
 
    Our principal executive office is located at 6933 South Revere Parkway,
Englewood, Colorado 80112, and our telephone number is (303) 476-4200 or (800)
RHYTHMS.
 
                                       6
<PAGE>
                                  THE OFFERING
 
<TABLE>
<S>                                            <C>
Common stock offered.........................  9,375,000 shares
 
Common stock to be outstanding after this
  offering...................................  70,564,582 shares(1)
 
Use of proceeds..............................  We will use the net proceeds to fund the
                                               continuing deployment of network services in
                                               our existing markets, as well as our planned
                                               rollout in additional markets. We also expect
                                               to use these proceeds for expenses associated
                                               with the continued development of our sales
                                               and marketing activities, to fund operating
                                               losses, to pay our debt obligations and for
                                               general corporate purposes.
 
Dividend policy..............................  We currently intend to retain any future
                                               earnings to fund the development of our
                                               business. Therefore, we do not currently
                                               anticipate paying cash dividends.
 
Nasdaq National Market symbol................  RTHM
</TABLE>
 
- ------------------------
 
(1) Based on the number of shares outstanding as of April 6, 1999. Includes
    51,076,051 shares of common stock to be issued upon conversion of our
    preferred stock and 5,598,989 shares of common stock which resulted from the
    exercise of stock options that remain unvested as of April 6, 1999. Excludes
    3,649,130 shares of common stock issuable upon the exercise of stock options
    outstanding as of April 6, 1999, with a weighted average exercise price of
    $8.70 per share, all of which are exercisable and 3,840 of which are vested,
    7,184,674 shares of common stock issuable upon the exercise of outstanding
    warrants, with a weighted average exercise price of $1.46 per share and
    456,595 shares of treasury stock. See "Capitalization" and "Business--Legal
    Proceedings."
 
                                       7
<PAGE>
                                  RISK FACTORS
 
    YOU SHOULD CAREFULLY CONSIDER THE RISKS AND UNCERTAINTIES DESCRIBED BELOW
AND THE OTHER INFORMATION IN THIS PROSPECTUS BEFORE DECIDING TO INVEST IN US.
YOU MAY LOSE ALL OR PART OF YOUR INVESTMENT. THE RISKS AND UNCERTAINTIES
DESCRIBED BELOW ARE NOT THE ONLY ONES FACING OUR COMPANY.
 
WE CANNOT PREDICT OUR SUCCESS BECAUSE WE HAVE A SHORT OPERATING HISTORY
 
    We formed our company in February 1997, and we have a short operating
history for you to review in evaluating our business. We have limited historical
financial and operating data upon which you can evaluate our business and
prospects. We entered into our first interconnection agreement with an incumbent
carrier in July 1997 and began to offer commercial services in San Diego in
April 1998. We have limited commercial operations and have recognized limited
revenues since our inception. In addition, our senior management team and our
other employees have worked together at our company for only a short period of
time.
 
BECAUSE OUR MARKET IS NEW AND EVOLVING, WE CANNOT PREDICT ITS FUTURE GROWTH OR
ULTIMATE SIZE, AND WE MAY BE UNABLE TO COMPETE EFFECTIVELY
 
    The market for packet-based high-speed digital communication services using
telephone lines is in the early stages of development. Since this market is new
and evolving and because our current and future competitors are likely to
introduce competing services, we cannot accurately predict the rate at which
this market will grow, if at all, or whether new or increased competition will
result in market saturation. Various providers of high-speed digital
communication services are testing products from various suppliers for various
applications, and suppliers have not broadly adopted an industry standard.
Certain critical issues concerning commercial use of DSL for Internet and local
area network access, including security, reliability, ease and cost of access
and quality of service, remain unresolved and may impact the growth of these
services. If the markets for our services fail to develop, grow more slowly than
anticipated or become saturated with competitors, these events could materially
and adversely affect our business, prospects, operating results and financial
condition.
 
    Our success will depend on the development of this new and rapidly evolving
market and our ability to compete effectively in this market. To address these
risks, we must, among other things:
 
    - rapidly expand the geographic coverage of our network services;
 
    - raise additional capital;
 
    - enter into interconnection agreements and working arrangements with
      additional incumbent carriers, substantially all of which we expect to be
      our competitors;
 
    - deploy an effective network infrastructure;
 
    - attract and retain customers;
 
    - successfully develop relationships and activities with our partners and
      distributors, including MCI WorldCom, Microsoft and Cisco;
 
    - continue to attract, retain and motivate qualified personnel;
 
    - accurately assess potential markets and effectively respond to competitive
      developments;
 
    - continue to develop and integrate our operational support system and other
      back office systems;
 
    - obtain any required governmental authorizations;
 
    - comply with evolving governmental regulatory requirements;
 
    - increase awareness of our services;
 
                                       8
<PAGE>
    - continue to upgrade our technologies; and
 
    - effectively manage our expanding operations.
 
    We may not be successful in addressing these and other risks, and our
failure to address risks would materially and adversely affect our business,
prospects, operating results and financial condition.
 
WE CANNOT PREDICT OUR SUCCESS BECAUSE OUR BUSINESS MODEL IS UNPROVEN
 
    We have not validated our business model and strategy in the market. We
believe that the combination of our unproven business model and the highly
competitive and fast changing market in which we compete makes it impossible to
predict the extent to which our network service will achieve market acceptance
and our overall success. To be successful, we must develop and market network
services that are widely accepted by businesses at profitable prices. We may
never be able to deploy our network as planned, achieve significant market
acceptance, favorable operating results or profitability or generate sufficient
cash flow to repay our debt. Of the 9,800 lines that we have committed to
deliver to date, we committed approximately 8,700 to only two customers. None of
our large business customers has rolled out our services broadly to its
employees, and we cannot be certain when or if these rollouts will occur. We
will not receive significant revenue from our large customers unless these
rollouts occur. Any continued or ongoing failure for any reason of large
business customers to roll out our services, failure to validate our business
model in the market, including failure to build out our network, achieve
widespread market acceptance or sustain desired pricing would materially and
adversely affect our business, prospects, operating results and financial
condition.
 
WE EXPECT OUR LOSSES TO CONTINUE
 
    We have incurred losses and experienced negative operating cash flow for
each month since our formation. As of December 31, 1998, we had an accumulated
deficit of approximately $38.8 million. We intend to rapidly and substantially
increase our expenditures and operating expenses in an effort to expand our
network services. We expect to have annual interest and amortization expense
relating to our senior discount notes of approximately $23.6 million in 1999 and
increasing to $39.5 million in 2003. In addition, we intend to seek additional
debt financing in the future. Furthermore, as a result of recent preferred stock
issuances and stock option grants, we anticipate that there will be significant
charges to earnings in future periods. As a result of these factors, we expect
to incur substantial operating and net losses and negative operating cash flow
for the foreseeable future. We will need to obtain additional financing to pay
our expenses and to make payments on our debt. We cannot give you any assurance
about whether or when we will have sufficient revenues to satisfy our funding
requirements or pay our debt service obligations.
 
OUR OPERATING RESULTS IN ONE OR MORE FUTURE PERIODS ARE LIKELY TO FLUCTUATE
SIGNIFICANTLY AND MAY FAIL TO MEET OR EXCEED THE EXPECTATIONS OF SECURITIES
ANALYSTS OR INVESTORS
 
    Our annual and quarterly operating results are likely to fluctuate
significantly in the future due to numerous factors, many of which are outside
of our control. These factors include:
 
    - the rate of customer acquisition and turnover;
 
    - the prices our customers are willing to pay;
 
    - the amount and timing of expenditures relating to the expansion of our
      services and infrastructure;
 
    - the timing and availability of incumbent carrier central office
      collocation facilities and transport facilities;
 
                                       9
<PAGE>
    - the success of our relationships with our partners and distributors,
      including MCI WorldCom, Microsoft and Cisco;
 
    - our ability to deploy our network on a timely basis;
 
    - introduction of new services or technologies by our competitors;
 
    - price competition;
 
    - the ability of our equipment and service suppliers to meet our needs;
 
    - regulatory developments, including interpretations of the 1996
      Telecommunications Act;
 
    - technical difficulties or network downtime;
 
    - the success of our strategic alliances; and
 
    - the condition of the telecommunication and network service industries and
      general economic conditions.
 
    Because of these factors, our operating results in one or more future
periods could fail to meet or exceed the expectations of securities analysts or
investors. In that event, the trading price of our common stock would likely
decline.
 
IF SALES FORECASTED FOR A PARTICULAR PERIOD ARE NOT REALIZED IN THAT PERIOD DUE
TO THE LENGTHY SALES CYCLE OF OUR SERVICES, OUR OPERATING RESULTS FOR THAT
PERIOD WILL BE HARMED
 
    The sales cycle of our network services can be very lengthy, particularly
for large businesses. The sales cycle for large businesses typically involves:
 
    - a significant technical evaluation;
 
    - an initial trial rollout to a relatively small number of end users;
 
    - a commitment of capital and other resources by the customer;
 
    - delays associated with the customer's internal procedures to approve large
      capital expenditures;
 
    - time required to engineer the deployment of our services;
 
    - coordination of the activation of multiple access lines with incumbent
      carriers; and
 
    - testing and acceptance of our services.
 
    For these and other reasons, our sales cycle for large businesses lasts at
least six months. During this lengthy sales cycle, we will incur significant
expenses in advance of the receipt of revenues. If sales that we forecast for a
particular period do not occur because of our lengthy sales cycle, this event
could materially and adversely affect our business, prospects, operating results
and financial condition.
 
WE DEPEND ON INCUMBENT CARRIERS FOR COLLOCATION AND TRANSMISSION FACILITIES
 
    We must use copper telephone lines controlled by the incumbent carriers to
provide DSL connections to customers. We also depend on the incumbent carriers
for collocation and for a substantial portion of the transmission facilities we
use to connect our equipment in incumbent carrier central offices to our Metro
Service Centers. In addition, we depend on the incumbent carriers to test and
maintain the quality of the copper lines that we use. We have not established a
history of obtaining access to collocation and transmission facilities from
incumbent carriers in large volumes. In many cases, we may be unable to obtain
access to collocation and transmission facilities from the incumbent carriers,
or to gain access at acceptable rates, terms and conditions, including
timeliness. We have experienced, and expect to experience in the future, lengthy
periods between our request for and the
 
                                       10
<PAGE>
actual provision of the collocation space and telephone lines. An inability to
obtain adequate and timely access to collocation space or transmission
facilities on acceptable terms and conditions from incumbent carriers could have
a material and adverse effect on our business, prospects, operating results and
financial condition.
 
    Because we compete with incumbent carriers in our markets, they may be
reluctant to cooperate with us. The incumbent carriers may experience, or claim
to experience, a shortage of collocation space or transmission capacity. If this
occurs, we may not have alternate means of connecting our DSL equipment with the
copper lines or connecting our equipment in central offices to Metro Service
Centers. We have experienced rejections of some of our collocation applications
on the grounds that no space is available. We may receive additional rejections
in the future. The number of other competitive local exchange carriers that
request collocation space will also affect the availability of collocation space
and transmission capacity. If we are unable to obtain physical collocation space
or transmission capacity from our targeted incumbent carriers, we may face
delays, additional costs or an inability to provide services in certain
locations. In many cases where our application for physical collocation is
rejected, we expect to have the option of adjacent location -- where we install
our equipment in a building that is very close to the incumbent carrier central
office -- or virtual collocation -- where the incumbent carrier manages and
operates our equipment. While we have used adjacent and virtual collocation in
our network, those alternatives reduce our control over our equipment, and
therefore may reduce the level of quality and service we provide to our
customers. We are currently in an arbitration proceeding with SBC Communications
Inc. concerning the availability of DSL-enabled copper lines, as well as other
operational issues. Delays in obtaining access to collocation space and
telephone lines or the rejection of our applications for collocation could
result in delays in, and increased expenses associated with, the rollout of our
services, which in turn could have a material and adverse effect on our
business, prospects, operating results and financial condition.
 
WE ARE UNABLE TO CONTROL THE TERMS AND CONDITIONS UNDER WHICH WE GAIN ACCESS TO
INCUMBENT CARRIER COLLOCATION AND TRANSMISSION FACILITIES
 
    We cannot control the terms under which we collocate our equipment, connect
to copper lines or gain the use of an incumbent carrier's transmission
facilities. State tariffs, state public utility commissions and interconnection
agreements with the incumbent carriers determine the price, terms and conditions
under which collocation space is made available, and they make these
administrative determinations in ongoing hearings. Interconnection agreements
and state public utility commissions also determine the terms and conditions of
access to copper lines and other components of an incumbent carrier's network.
We may be unable to negotiate or enter into interconnection agreements on
acceptable terms or at all. In addition, we cannot be sure that incumbent
carriers will abide by their obligations under those agreements. Delays in
obtaining interconnection agreements would delay our entry into certain markets.
In addition, disputes may arise between us and the incumbent carriers with
respect to interconnection agreements, and we may be unable to resolve disputes
in our favor. If we are unable to enter into, or experience a delay in
obtaining, interconnection agreements, this inability or delay could adversely
affect our business, prospects, operating results and financial condition.
Further, the interconnection agreements are generally short term, and we may be
unable to renew the interconnection agreements on acceptable terms or at all.
The state commissions, the Federal Communications Commission and the courts
oversee, in varying degrees, interconnection arrangements as well as the terms
and conditions under which we gain access to incumbent carrier copper lines and
transmission facilities. These government entities may modify the terms or
prices of our interconnection agreements and our access to incumbent carrier
copper lines and transmission facilities in ways that would be adverse to our
business. State regulatory commissions establish the price rates for DSL-capable
copper lines as well as other rates, terms and conditions of our dealings with
the incumbent carriers in ongoing public hearings. Participation in these
hearings will involve significant management time and expense. Incumbent
carriers may from time to time propose new rates, and the
 
                                       11
<PAGE>
outcomes of hearings and rulings could have a material and adverse effect on our
business, prospects, operating results and financial condition.
 
WE DEPEND ON THIRD PARTIES, PARTICULARLY MCI WORLDCOM, MICROSOFT AND CISCO, FOR
THE MARKETING AND SALES OF OUR NETWORK SERVICES
 
    We will rely significantly on indirect sales channels for the marketing and
sales of our network services. We will seek to establish relationships with
numerous service providers, including Internet Service Providers, interexchange
carriers, other competitive carriers and value-added resellers, to gain access
to customers. Our agreements to date with service providers are non-exclusive,
and we anticipate that future agreements will also be on a non-exclusive basis,
allowing service providers to resell services offered by our competitors. These
agreements are generally short term, and can be cancelled by the service
provider without significant financial consequence. We cannot control how these
service providers perform and cannot be certain that their performance will be
satisfactory to us or our customers. Many of these companies also compete with
us. If the number of customers we obtain through indirect sales channels is
significantly lower than our forecast for any reason, or if the service
providers with which we have contracted are unsuccessful in competing in their
own intensely competitive markets, these events would have a material and
adverse effect on our business, prospects, operating results and financial
condition.
 
    We expect to rely particularly on the sales and marketing efforts of our
strategic partners, including MCI WorldCom, Microsoft and Cisco. While our
agreement with MCI WorldCom calls for it to sell 100,000 DSL lines, the
agreement also enables MCI WorldCom to terminate the agreement under certain
circumstances and to receive offsets and credits under other circumstances.
Therefore, MCI WorldCom might sell significantly fewer than 100,000 DSL lines,
or we might receive significantly lower revenues than we otherwise would.
 
THE MARKET IN WHICH WE OPERATE IS HIGHLY COMPETITIVE, AND WE MAY NOT BE ABLE TO
COMPETE EFFECTIVELY, ESPECIALLY AGAINST ESTABLISHED INDUSTRY COMPETITORS WITH
SIGNIFICANTLY GREATER FINANCIAL RESOURCES
 
    We will face competition from many competitors with significantly greater
financial resources, well-established brand names and large, existing installed
customer bases. We expect the level of competition to intensify in the future.
We expect significant competition from incumbent carriers, traditional and new
long distance carriers, cable modem service providers, Internet Service
Providers, wireless and satellite data service providers and other competitive
carriers. Incumbent carriers have existing metropolitan area networks and
circuit-switched local access networks. In addition, most incumbent carriers are
establishing their own Internet Service Provider businesses and are in some
stage of market trials and retail sales of DSL-based access services. Some
incumbent carriers have announced that they intend to aggressively market these
services to their residential customers at attractive prices. We believe that
incumbent carriers have the potential to quickly overcome many of the issues
that have delayed widespread deployment of DSL services in the past. In
addition, we may experience substantial customer turnover in the future. Many
providers of telecommunications and networking services experience high rates of
customer turnover.
 
    Many of the leading traditional long distance carriers, including AT&T
Corporation, MCI WorldCom and Sprint, are expanding their capabilities to
support high-speed, end-to-end networking services. The newer long distance
carriers, including Williams Companies Inc., Qwest Communications International,
Inc. and Level 3 Communications, Inc., are building and managing high bandwidth,
nationwide packet networks and partnering with Internet Service Providers to
offer services directly to the public. Cable modem service providers, like @Home
Networks, are offering or preparing to offer high-speed Internet access over
hybrid fiber networks to consumers, and @Work positioned itself to do the same
for businesses. Several new companies are emerging as wireless, including
satellite-based, data
 
                                       12
<PAGE>
service providers. Internet Service Providers, including some with significant
and even nationwide presences, provide Internet access to residential and
business customers, generally over the incumbent carriers' circuit switched
networks, although some have begun offering DSL-based access. Certain
competitive carriers, including Covad Communications Group, Inc. and NorthPoint
Communications, Inc., have begun offering DSL-based access services, and, like
us, have attracted strategic equity investors, marketing allies and product
development partners. Others are likely to do the same in the future.
 
    Many of these competitors are offering, or may soon offer, technologies and
services that will directly compete with some or all of our service offerings.
Some of the technologies used by these competitors for local access connections
include integrated services digital network (ISDN), DSL, wireless data and cable
modems. Some of the competitive factors in our markets include transmission
speed, reliability of service, breadth of service availability, price
performance, network security, ease of access and use, content bundling,
customer support, brand recognition, operating experience, capital availability
and exclusive contracts. We believe that we compare unfavorably with many of our
competitors with regard to, among other things, brand recognition, existing
relationships with end users, available pricing discounts, central office
access, capital availability and exclusive contracts. Substantially all of our
competitors and potential competitors have substantially greater resources than
us. We may not be able to compete effectively in our target markets. Our failure
to compete effectively would have a material and adverse effect on our business,
prospects, operating results and financial condition. See
"Business--Competition."
 
OUR NETWORK SERVICES MAY NOT ACHIEVE SIGNIFICANT MARKET ACCEPTANCE BECAUSE OUR
PRICES ARE OFTEN HIGHER THAN THOSE CHARGED FOR COMPETING SERVICES
 
    Our prices are in some cases higher than those that our competitors charge
for some of their services. Prices for digital communications services have
fallen historically, and we expect prices in the industry in general, and for
the services we offer now and plan to offer in the future, to continue to fall.
We may be required to reduce prices periodically to respond to competition and
to generate increased sales volume. Our prices may not permit our network
services to gain a desirable level of commercial acceptance, and we may be
unable to sustain any current or future pricing levels. Due to these factors, we
cannot accurately forecast our revenues or the rate at which we will add new
customers.
 
WE WILL NEED SIGNIFICANT ADDITIONAL FUNDS, WHICH WE MAY NOT BE ABLE TO OBTAIN
 
    The expansion and development of our business will require significant
additional capital. We intend to seek substantial additional financing in the
future to fund the growth of our operations, including funding the significant
capital expenditures and working capital requirements necessary for us to
provide service in our targeted markets. We believe that our current capital
resources, including the proceeds of this offering, will be sufficient to fund
our aggregate capital expenditures and working capital requirements, including
operating losses, until June 2000. We will not have completed our network
rollout by this date and will need additional capital, whether or not our
estimate on how long current capital resources will last is accurate. In
addition, our actual funding requirements may differ materially if our
assumptions underlying this estimate turn out to be incorrect. Therefore, you
should consider our estimate in light of the following facts:
 
    - we have no meaningful history of operations or revenues;
 
    - our estimated funding requirements do not reflect any contingency amounts
      and may increase, perhaps substantially, if we are unable to generate
      revenues in the amount and within the time frame we expect or if we have
      unexpected cost increases; and
 
    - we face many challenges and risks, including those discussed elsewhere in
      "Risk Factors."
 
                                       13
<PAGE>
    We may be unable to obtain any future equity or debt financing on acceptable
terms or at all. Recently the financial markets have experienced extreme price
fluctuations. A market downturn or general market uncertainty may adversely
affect our ability to secure additional financing. The indenture that governs
our senior discount notes restricts our ability to obtain additional debt
financing. Any future borrowing instruments, such as credit facilities and lease
agreements, are likely to contain similar or more restrictive covenants and
could require us to pledge assets as security for the borrowings. If we are
unable to obtain additional capital or are required to obtain it on terms less
satisfactory than what we desire, we will need to delay deployment of our
network services or take other actions that could adversely affect our business,
prospects, operating results and financial condition. If we are unable to
generate sufficient cash flow or obtain funds necessary to meet required
payments of our debt, then we will be in default on our debt instruments. To
date, our cash flow from operations has been insufficient to cover our expenses
and capital needs. Please see "Management's Discussion and Analysis of Financial
Condition and Results of Operations--Liquidity and Capital Resources."
 
OUR SERVICES ARE SUBJECT TO GOVERNMENT REGULATION, AND CHANGES IN CURRENT OR
FUTURE LAWS OR REGULATIONS COULD RESTRICT THE WAY WE OPERATE OUR BUSINESS
 
    A significant portion of the services that we offer through our subsidiaries
is subject to regulation at the federal, state and/or local levels. Future
federal or state regulations and legislation may be less favorable to us than
current regulation and legislation and therefore have an adverse impact on our
business, prospects, operating results and financial condition. In addition, we
may expend significant financial and managerial resources to participate in
rule-setting proceedings at either the federal or state level, without achieving
a favorable result. The Federal Communications Commission
prescribes rules applicable to interstate communications, including rules
implementing the 1996 Telecommunications Act, a responsibility it shares with
the state regulatory commissions. In particular, we believe that incumbent
carriers will work aggressively to modify or restrict the operation of many
provisions of the 1996 Telecommunications Act. We expect incumbent carriers will
pursue litigation in courts, institute administrative proceedings with the
Federal Communications Commission and other regulatory agencies and lobby the
United States Congress, all in an effort to affect laws and regulations in a
manner favorable to the incumbent carriers and against the interest of
competitive carriers such as us. If the incumbent carriers succeed in any of
their efforts, if these laws and regulations change or if the administrative
implementation of laws develops in an adverse manner, these events could have a
material and adverse effect on our business, prospects, operating results and
financial condition. For more details about our regulatory situation, please see
"Business--Government Regulation."
 
OUR FAILURE TO MANAGE GROWTH COULD ADVERSELY AFFECT US
 
    We have rapidly and significantly expanded our operations. We anticipate
further significant expansion of our operations in an effort to achieve our
network rollout and deployment objectives. Our expansion to date has strained
our management, financial controls, operations systems, personnel and other
resources. Any future rapid expansion would increase these strains. If our
marketing strategy is successful, we may experience difficulties responding to
customer demand for services and technical support in a timely manner and in
accordance with their expectations. As a result, rapid growth of our business
would make it difficult to implement successfully our strategy to provide
superior customer service. To manage any growth of our operations, we must:
 
    - improve existing and implement new operational, financial and management
      information controls, reporting systems and procedures;
 
    - hire, train and manage additional qualified personnel;
 
    - expand and upgrade our core technologies; and
 
    - effectively manage multiple relationships with our customers, suppliers
      and other third parties.
 
                                       14
<PAGE>
    We may not be able to install management information and control systems in
an efficient and timely manner, and our current or planned personnel, systems,
procedures and controls may not be adequate to support our future operations.
Failure to manage our future growth effectively could adversely affect the
expansion of our customer base and service offerings. Any failure to
successfully address these issues could materially and adversely affect our
business, prospects, operating results and financial condition.
 
OUR SUBSTANTIAL DEBT CREATES FINANCIAL AND OPERATING RISK
 
    We are highly leveraged, and we intend to seek additional debt funding in
the future. As of December 31, 1998, we had approximately $158.3 million of
outstanding debt, and our debt made up 100% of our capitalization. Please see
"Capitalization." We are not generating any meaningful revenue to fund our
operations or to repay our debt. Our substantial leverage poses the risks that:
 
    - we may be unable to repay our debt due to one or more events discussed in
      "Risk Factors;"
 
    - we may be unable to obtain additional financing;
 
    - we must dedicate a substantial portion of our cash flow from operations to
      servicing our debt once our debt requires us to make cash interest
      payments, and any remaining cash flow may not be adequate to fund our
      planned operations; and
 
    - we may be more vulnerable during economic downturns, less able to
      withstand competitive pressures and less flexible in responding to
      changing business and economic conditions.
 
THE TELECOMMUNICATIONS INDUSTRY IS UNDERGOING RAPID TECHNOLOGICAL CHANGE, AND
NEW TECHNOLOGIES MAY BE SUPERIOR TO THE TECHNOLOGY WE USE
 
    The telecommunications industry is subject to rapid and significant
technological changes, such as continuing developments in DSL technology and
alternative technologies for providing high-speed data communications. We cannot
predict the effect of technological changes on our business. We will rely in
part on third parties, including certain of our competitors and potential
competitors, for the development of and access to communications and networking
technology. We expect that new products and technologies applicable to our
market will emerge. New products and technologies may be superior and/or render
obsolete the products and technologies that we currently use. Our future success
will depend, in part, on our ability to anticipate and adapt to technological
changes and evolving industry standards. We may be unable to obtain access to
new technology on acceptable terms or at all, and we may be unable to adapt to
new technologies and offer services in a competitive manner. Our joint
development projects with Cisco and MCI WorldCom and our strategic arrangement
with Microsoft may not produce useful technologies or services for us. Further,
new technologies and products may not be compatible with our technologies and
business plan. We believe that the telecommunications industry must set
standards to allow for the compatibility of various products and technologies.
However, the industry may not set standards on a timely basis or at all. In
addition, many of the products and technologies that we intend to use in our
network services are relatively new and unproven and may be unreliable.
 
WE MAY BE UNABLE TO EFFECTIVELY EXPAND OUR NETWORK SERVICES AND PROVIDE HIGH
PERFORMANCE TO A SUBSTANTIAL NUMBER OF END USERS
 
    Due to the limited deployment of our network services, we cannot guarantee
that our network will be able to connect and manage a substantial number of end
users at high transmission speeds. We may be unable to scale our network to
service a substantial number of end users while achieving high performance.
Further, our network may be unable to achieve and maintain competitive digital
transmission speeds. While digital transmission speeds of up to 7.1 Mbps are
possible on certain portions of our network, that speed is not available over a
majority of our network. Actual transmission
 
                                       15
<PAGE>
speeds on our network will depend on a variety of factors and many of these
factors are beyond our control, including the type of DSL technology deployed,
the distance an end user is located from a central office, the quality of the
telephone lines, the presence of interfering transmissions on nearby lines and
other factors. As a result, we may not be able to achieve and maintain digital
transmission speeds that are attractive in the market.
 
OUR SERVICES MAY SUFFER BECAUSE THE TELEPHONE LINES WE REQUIRE MAY BE
UNAVAILABLE OR IN POOR CONDITION
 
    Our ability to provide DSL-based services to potential customers depends on
the quality, physical condition, availability and maintenance of telephone lines
within the control of the incumbent carriers. We believe that the current
condition of telephone lines in many cases will be inadequate to permit us to
fully implement our network services. In addition, the incumbent carriers may
not maintain the telephone lines in a condition that will allow us to implement
our network effectively. The telephone lines may not be of sufficient quality or
the incumbent carriers may claim they are not of sufficient quality to allow us
to fully implement or operate our network services. Further, some customers use
technologies other than copper lines to provide telephone services, and DSL
might not be available to these customers.
 
OUR SUCCESS DEPENDS ON OUR RETENTION OF CERTAIN KEY PERSONNEL AND ON THE
PERFORMANCE OF THOSE PERSONNEL
 
    Our success depends on the performance of our officers and key employees,
especially our Chief Executive Officer. Members of our senior management team
have worked together for only a short period of time. We do not have "key
person" life insurance policies on any of our employees nor do we have
employment agreements for fixed terms with any of our employees. Any of our
employees, including any member of our senior management team, may terminate his
or her employment with us at any time. Given our early stage of development, we
depend on our ability to retain and motivate high quality personnel, especially
our management. Our future success also depends on our continuing ability to
identify, hire, train and retain highly qualified technical, sales, marketing
and customer service personnel. Moreover, the industry in which we compete has a
high level of employee mobility and aggressive recruiting of skilled personnel.
We may be unable to continue to employ our key personnel or to attract and
retain qualified personnel in the future. We face intense competition for
qualified personnel, particularly in software development, network engineering
and product management. Please see "Business--Employees" and "Management."
 
WE DEPEND ON THIRD PARTIES FOR EQUIPMENT, INSTALLATION AND PROVISION OF FIELD
SERVICE
 
    We currently plan to purchase all of our equipment from many vendors and
outsource the majority of the installation and field service of our networks to
third parties. Our reliance on third party vendors involves a number of risks,
including the absence of guaranteed capacity and reduced control over delivery
schedules, quality assurance, production yields and costs. If any of our
suppliers reduces or interrupts its supply, or if any significant installer or
field service provider interrupts its service to us, this reduction or
interruption could disrupt our business. Although multiple manufacturers
currently produce or are developing equipment that will meet our current and
anticipated requirements, our suppliers may be unable to manufacture and deliver
the amount of equipment we order, or the available supply may be insufficient to
meet our demand. Currently, almost all of the DSL modem and DSL multiplexing
equipment we use for a single connection over a copper line must come from the
same vendor since there are no existing interoperability standards for the
equipment used in our higher speed services. If our suppliers or licensors enter
into competition with us, or if our competitors enter into exclusive or
restrictive arrangements with the suppliers or licensors, then these events may
materially and adversely affect the availability and pricing of the equipment we
purchase and the technology we license.
 
                                       16
<PAGE>
A SYSTEM FAILURE OR BREACH OF NETWORK SECURITY COULD CAUSE DELAYS OR
INTERRUPTIONS OF SERVICE TO OUR CUSTOMERS
 
    Our operations depend on our ability to avoid damages from fires,
earthquakes, floods, power losses, excessive sustained or peak user demand,
telecommunications failures, network software flaws, transmission cable cuts and
similar events. A natural disaster or other unanticipated problem at our owned
or leased facilities could interrupt our services. Additionally, if an incumbent
carrier, competitive carrier or other service provider fails to provide the
communications capacity we require, as a result of a natural disaster,
operational disruption or any other reason, then this failure could interrupt
our services.
 
    Despite the implementation of security measures, our network may be
vulnerable to unauthorized access, computer viruses and other disruptive
problems. Corporate networks and Internet Service Providers have in the past
experienced, and may in the future experience, interruptions in service as a
result of accidental or intentional actions of Internet users, current and
former employees and others. Unauthorized access could also potentially
jeopardize the security of confidential information stored in the computer
systems of our customers, which might cause us to be liable to our customers,
and also might deter potential customers. Eliminating computer viruses and
alleviating other security problems may require interruptions, delays or
cessation of service to our customers and our customers' end users.
 
INTERFERENCE OR CLAIMS OF INTERFERENCE COULD DELAY OUR ROLLOUT OR HARM OUR
SERVICES
 
    All transport technologies deployed on copper telephone lines have the
potential to interfere with, or to be interfered with by, other transport
technologies on the copper telephone lines. We believe that our DSL
technologies, like other transport technologies, do not interfere with existing
voice services. We believe that a workable plan that takes into account all
technologies could be implemented in a scalable way across all incumbent
carriers using existing plant engineering principles. There are several
initiatives underway to establish national standards and principles for the
deployment of DSL technologies. We believe that our technologies can be deployed
consistently with these evolving standards. Nevertheless, incumbent carriers may
claim that the potential for interference permits them to restrict or delay our
deployment of DSL services. Interference could degrade the performance of our
services or make us unable to provide service on selected lines. The procedures
to resolve interference issues between competitive carriers and incumbent
carriers are still being developed, and these procedures may not be effective.
We may be unable to successfully negotiate interference resolution procedures
with incumbent carriers. Moreover, incumbent carriers may make claims regarding
interference or unilaterally take action to resolve interference issues to the
detriment of our services. State or federal regulators could also institute
responsive actions. Interference, or claims of interference, if widespread,
would adversely affect our speed of deployment, reputation, brand image, service
quality and customer satisfaction and retention.
 
WE DEPEND ON THIRD PARTIES FOR FIBER OPTIC TRANSPORT FACILITIES
 
    We depend on the availability of fiber optic transmission facilities from
third parties to connect our equipment within and between metropolitan areas.
These third party fiber optic carriers include long distance carriers, incumbent
carriers and other competitive carriers. Many of these entities are, or may
become, our competitors. This approach includes a number of risks. For instance,
we may be unable to negotiate and renew favorable supply agreements. Further, we
depend on the timeliness of these companies to process our orders for customers
who seek to use our services. We have in the past experienced supply problems
with certain of our fiber optic suppliers, and they may not be able to meet our
needs on a timely basis in the future. Moreover, the fiber optic transport
providers whose networks we lease may be unable to obtain or maintain permits
and rights-of-way necessary to develop and operate existing and future networks.
 
                                       17
<PAGE>
UNCERTAIN FEDERAL AND STATE TAX AND OTHER SURCHARGES ON OUR SERVICES MAY
INCREASE OUR PAYMENT OBLIGATIONS
 
    Telecommunications providers pay a variety of surcharges and fees on their
gross revenues from interstate and intrastate services. The division of our
services between interstate and intrastate services is a matter of
interpretation, and in the future the Federal Communications Commission or
relevant state commission authorities may contest this division. A change in the
characterization of the jurisdiction of our services could cause our payment
obligations to increase. In addition, pursuant to periodic revisions by state
and federal regulators of the applicable surcharges, we may be subject to
increases in the surcharges and fees currently paid.
 
OUR INTELLECTUAL PROPERTY PROTECTION MAY BE INADEQUATE TO PROTECT OUR
PROPRIETARY RIGHTS, AND WE MAY BE SUBJECT TO INFRINGEMENT CLAIMS
 
    We rely on a combination of licenses, confidentiality agreements and other
contracts to establish and protect our technology and other intellectual
property rights. We have applied for trademarks and servicemarks on certain
terms and symbols that we believe are important for our business. We currently
have no patents or patent applications pending. The steps we have taken may be
inadequate to protect our technology or other intellectual property. Moreover,
our competitors may independently develop technologies that are substantially
equivalent or superior to ours. Third parties may assert infringement claims
against us and, in the event of an unfavorable ruling on any claim, we may be
unable to obtain a license or similar agreement to use technology we rely upon
to conduct our business. We also rely on unpatented trade secrets and know-how
to maintain our competitive positions, which we seek to protect, in part, by
confidentiality agreements with employees, consultants and others. However,
these agreements may be breached or terminated, and we may not have adequate
remedies for any breach. In addition, our competitors may otherwise learn or
discover our trade secrets. Our management personnel were previously employees
of other telecommunications companies. In many cases, these individuals are
conducting activities for us in areas similar to those in which they were
involved prior to joining us. As a result, we or our employees could be subject
to allegations of violation of trade secrets and other similar claims.
 
RISKS ASSOCIATED WITH POTENTIAL GENERAL ECONOMIC DOWNTURN
 
    In the last few years the general health of the economy, particularly the
economy of California where we have conducted a significant portion of our
operations to date, has been relatively strong and growing, a consequence of
which has been increasing capital spending by individuals and growing companies
to keep pace with rapid technological advances. To the extent the general
economic health of the United States or of California declines from recent
historically high levels, or to the extent individuals or companies fear a
decline is imminent, these individuals and companies may reduce expenditures
such as those for our services. Any decline or concern about an imminent decline
could delay decisions among certain of our customers to roll out our services or
could delay decisions by prospective customers to make initial evaluations of
our services. Any delays would have a material and adverse effect on our
business, prospects, operating results and financial condition.
 
WE MAY BE UNABLE TO SATISFY, OR MAY BE ADVERSELY CONSTRAINED BY, THE COVENANTS
IN OUR EXISTING DEBT SECURITIES
 
    The indenture for our senior discount notes imposes significant restrictions
on how we can conduct our business. For example, the restrictions prohibit or
limit our ability to incur additional debt, make dividend payments and engage in
certain business activities. The restrictions may materially and
 
                                       18
<PAGE>
adversely affect our ability to finance future operations or capital needs or
conduct additional business activities. Any future senior debt that we may incur
will likely impose additional restrictions on us. If we fail to comply with any
existing or future restrictions, we could default under the terms of the
applicable debt and be unable to meet our debt obligations. If we default, the
holders of the applicable debt could demand that we pay the debt, including
interest, immediately. We may be unable to make the required payments or raise
sufficient funds from alternative sources to make the payments. Even if
additional financing is available in the event that we default, it may not be on
acceptable terms.
 
OUR PRINCIPAL STOCKHOLDERS AND MANAGEMENT OWN A SIGNIFICANT PERCENTAGE OF OUR
COMPANY, AND WILL BE ABLE TO EXERCISE SIGNIFICANT INFLUENCE OVER OUR COMPANY
 
    Our executive officers and directors and principal stockholders together
will beneficially own 81.4% of the common stock after completion of this
offering, or 79.8% if the over-allotment option is exercised in full.
Accordingly, these stockholders will be able to determine the composition of our
Board of Directors, will retain the voting power to approve all matters
requiring stockholder approval and will continue to have significant influence
over our affairs. This concentration of ownership could have the effect of
delaying or preventing a change in our control or otherwise discouraging a
potential acquirer from attempting to obtain control of us, which in turn could
have a material and adverse effect on the market price of the common stock or
prevent our stockholders from realizing a premium over the market prices for
their shares of common stock. See "Principal Stockholders" for information about
the ownership of common stock by our executive officers, directors and principal
stockholders.
 
OUR FAILURE AND THE FAILURE OF THIRD PARTIES TO BE YEAR 2000 COMPLIANT COULD
NEGATIVELY IMPACT OUR BUSINESS
 
    Many computer programs have been written using two digits rather than four
to define the applicable year. This poses a problem at the end of the century
because these computer programs may recognize a date using "00" as the year 1900
rather than the year 2000. This, in turn, could result in major system failures
or miscalculations, and is generally referred to as the "Year 2000 issue." We
have formulated and, to a large extent, effected a plan to address our Year 2000
issues.
 
    Our Year 2000 plan applies to two areas: internal business systems and
compliance by external customers and providers. We have completed our Year 2000
compliance testing for all of our internal systems and believe that they are
Year 2000 compliant. Because we are a young company, we believe we have been
able to build our business systems with the Year 2000 issue in mind in a more
effective manner than many older companies. Therefore, there have been few Year
2000 changes required to our existing systems and applications. We have
substantially completed a compliance check of our external customers and
providers, except for the incumbent carriers. Based on responses from these
third parties, other than the incumbent carriers, we believe that they will not
experience Year 2000 problems that would materially and adversely affect our
business. We have not been able to conduct a compliance check of incumbent
carriers nor assess the incumbent carriers' Year 2000 compliance. To the extent
that one or more incumbent carriers or other third parties experience Year 2000
problems, our network and services could be adversely affected. Furthermore, the
purchasing patterns of our customers may be affected by Year 2000 issues as
companies expend significant resources to correct their current systems for Year
2000 compliance. These expenditures may result in reduced funds available for
our services. Any of these developments could have a material and adverse effect
on our business, prospects, operating results and financial condition. We have
not fully determined the risks associated with the reasonably worst-case
scenario and have not formulated a contingency plan to address Year 2000 issues.
We do not expect to have a specific contingency plan in place in the future.
 
                                       19
<PAGE>
IF WE ARE REQUIRED TO REGISTER AS AN INVESTMENT COMPANY, WE WOULD BECOME SUBJECT
TO SUBSTANTIAL REGULATION WHICH WOULD INTERFERE WITH OUR ABILITY TO CONDUCT OUR
BUSINESS ACCORDING TO OUR BUSINESS PLAN
 
    As a result of this offering and our previous financings, we have
substantial cash, cash equivalents and short-term investments. We plan to
continue investing the excess proceeds of these financings in short-term
instruments consistent with prudent cash management and not primarily for the
purpose of achieving investment returns. Please see "Use of Proceeds."
Investment in securities primarily for the purpose of achieving investment
returns could result in our being treated as an "investment company" under the
Investment Company Act of 1940. The Investment Company Act requires the
registration of companies that are primarily in the business of investing,
reinvesting or trading securities or that fail to meet certain statistical tests
regarding their composition of assets and sources of income even though they
consider themselves not to be primarily engaged in investing, reinvesting or
trading securities.
 
    We believe that we are primarily engaged in a business other than investing
in or trading securities and, therefore, are not an investment company within
the meaning of the Investment Company Act. If the Investment Company Act
required us to register as an investment company, we would become subject to
substantial regulation with respect to our capital structure, management,
operations, transactions with affiliated persons and other matters. Application
of the provisions of the Investment Company Act to us would materially and
adversely affect our business, prospects, operating results and financial
condition.
 
WE EXPECT OUR STOCK PRICE TO BE VOLATILE
 
    The price at which our common stock will trade will depend upon many
factors, including our historical and anticipated quarterly and annual operating
results, variations between our actual results and analyst and investor
expectations, announcements by us or others and developments affecting our
business, investor perceptions of our company and comparable public companies,
changes in our industry and general market and economic conditions. Some of
these factors are beyond our control. You should be aware that the stock market
has from time to time experienced extreme price and volume fluctuations.
 
WE HAVE NOT PAID AND DO NOT INTEND TO PAY DIVIDENDS
 
    We have not paid any dividends, and we do not intend to pay cash dividends
in the foreseeable future. Our current financing documents contain provisions
which restrict our ability to pay dividends.
 
THERE HAS BEEN NO PRIOR MARKET FOR THE COMMON STOCK
 
    Before this offering, there has not been a public market for the common
stock. We will apply to the Nasdaq National Market System to list our common
stock, but we do not know whether active trading in the common stock will
develop and continue after the offering. We will determine the initial public
offering price for the common stock through negotiations with the underwriters.
You may not be able to resell your shares at or above the initial public
offering price. For a description of the factors that will be taken into account
to determine the offering price, please see "Underwriting."
 
ANTI-TAKEOVER PROVISIONS COULD NEGATIVELY IMPACT OUR STOCKHOLDERS
 
    Our Board of Directors has adopted a stockholder rights plan. Our
stockholder rights plan would cause substantial dilution to any person or group
that attempts to acquire our company on terms not approved in advance by our
Board of Directors. In addition, some of the provisions that may be included in
our certificate of incorporation and bylaws may discourage, delay or prevent a
merger or acquisition at a premium price. These provisions include:
 
    - authorizing the issuance of "blank check" preferred stock;
 
                                       20
<PAGE>
    - providing for a classified Board of Directors with staggered, three-year
      terms;
 
    - eliminating the ability of stockholders to call a special meeting of
      stockholders;
 
    - limiting the removal of directors by the stockholders to removal for
      cause; and
 
    - requiring a super-majority stockholder vote to effect certain amendments.
 
In addition, certain provisions of the Delaware General Corporation Law and our
stockholder rights plan may deter someone from acquiring or merging with us,
including a transaction that results in stockholders receiving a premium over
the market price for the shares of common stock held by them. Section 203 of the
Delaware General Corporation Law also imposes certain restrictions on mergers
and other business combinations between us and any holder of more than 15% and
less than 85% of our common stock. See "Description of Capital Stock--Possible
Anti-Takeover Matters."
 
    The indenture governing our senior discount notes requires us to offer to
repurchase all senior discount notes for 101% of their principal amount or
accreted value, plus any accrued interest due, within 30 days after a change of
control. See "Description of Certain Indebtedness." We might not have sufficient
funds available at the time of any change of control to make any required
payment, as well as any payment that may be required pursuant to any other
outstanding indebtedness at the time, including our indebtedness to equipment
financing lenders. These covenants may also deter third parties from entering
into a change of control transaction with us. Furthermore, following the
occurrence of certain change-of-control events, we must offer to repurchase for
cash all of the outstanding warrants issued in connection with the senior
discount notes.
 
THE PRICE OF OUR COMMON STOCK MAY DECLINE DUE TO SHARES ELIGIBLE FOR FUTURE SALE
 
    Sales of substantial amounts of common stock in the public market following
this offering, or the appearance that a large number of shares is available for
sale, could adversely affect the market price for the common stock. The number
of shares of common stock available for sale in the public market will be
limited by lock-up agreements under which the holders of substantially all of
our outstanding shares of common stock and options and warrants to purchase
common stock will agree not to sell or otherwise dispose of any of their shares
for a period of 180 days after the date of this prospectus without the prior
written consent of Merrill Lynch and Salomon Smith Barney. However, Merrill
Lynch and Salomon Smith Barney may, in their sole discretion and at any time
without notice, release all or any portion of the securities subject to lock-up
agreements. In addition to the adverse effect a price decline could have on
holders of common stock, that decline would likely impede our ability to raise
capital through the issuance of additional shares of common stock or other
equity securities. See "Description of Capital Stock--Registration Rights" and
"Shares Eligible for Future Sale."
 
YOU WILL INCUR IMMEDIATE AND SUBSTANTIAL DILUTION OF APPROXIMATELY $17.34 PER
SHARE
 
    The initial public offering price is substantially higher than the net
tangible book value per share of the outstanding common stock immediately after
this offering. Accordingly, if you purchase common stock in this offering, you
will incur immediate and substantial dilution of $17.34 in the net tangible book
value per share of the common stock from the price you pay for the common stock
in this offering.
 
MANAGEMENT HAS BROAD DISCRETION TO USE THE PROCEEDS FROM THIS OFFERING
 
    Our management will have broad discretion over the use of proceeds we raise
in this offering, and you must rely on the judgment of management in the
application of the proceeds. Please see "Use of Proceeds" for more information
related to our financing plan.
 
                                       21
<PAGE>
                                USE OF PROCEEDS
 
    We will use the aggregate net proceeds of this offering, which we estimate
at approximately $182.3 million after deducting the underwriters' discount and
other estimated offering expenses, to fund the expenditures incurred in the
continuing deployment of network services in our existing markets, as well as
our planned rollout in additional markets. Additionally, we plan to use the net
proceeds from this offering for expenses associated with the continued
development of our sales and marketing activities, to fund operating losses, to
pay our debt obligations and for general corporate purposes. Pending use of such
net proceeds, we intend to invest the net proceeds in short-term, investment
grade securities to the extent permitted by the terms of the covenants governing
our existing debt and any statistical asset tests imposed by the Investment
Company Act of 1940.
 
    The actual amounts we spend will vary significantly depending upon a number
of factors, including future revenue growth, if any, capital expenditures, the
amount of cash generated by our operations and other factors, many of which are
beyond our control. Additionally, we may modify the number, selection and timing
of our entry with respect to any or all of our targeted markets. Accordingly,
our management will retain broad discretion in the allocation of the net
proceeds. Please see "Risk Factors--We will need significant additional funds,
which we may not be able to obtain" and "Management's Discussion and Analysis of
Financial Condition and Results of Operations."
 
                                DIVIDEND POLICY
 
    We have never declared or paid dividends on our capital stock, and we do not
anticipate paying any cash dividends in the foreseeable future. Payments of any
future dividends will be at the discretion of our Board of Directors after
taking into account various factors, such as our financial condition, operating
results, current and anticipated cash needs and plans for expansion.
 
                                       22
<PAGE>
                                 CAPITALIZATION
 
    The following unaudited table sets forth our capitalization as of December
31, 1998:
 
    - on an actual basis;
 
    - pro forma to give effect to the issuance of Series C preferred stock and
      warrants to MCI WorldCom's investment fund on March 4, 1999 and to
      Microsoft on March 16, 1999, the issuance of Series C preferred stock and
      Series D preferred stock and warrants to Qwest's subsidiary on April 6,
      1999, and the issuance of warrants to GATX on March 31, 1999, to Cisco
      Systems Capital Corporation in April 1999 and to MCI WorldCom's investment
      fund on April 6, 1999; and
 
    - pro forma as adjusted to give effect to this offering, including
      conversion of the existing Series A, Series B, Series C and Series D
      preferred stock into common stock which will occur automatically upon the
      completion of this offering.
 
    Please read this table in conjunction with our consolidated financial
statements, the related notes to the financial statements and "Management's
Discussion and Analysis of Financial Condition and Results of Operations"
included elsewhere in this prospectus.
 
<TABLE>
<CAPTION>
                                                                                               AS OF
                                                                                         DECEMBER 31, 1998
                                                                                -----------------------------------
                                                                                                         PRO FORMA
                                                                                 ACTUAL     PRO FORMA   AS ADJUSTED
                                                                                ---------  -----------  -----------
                                                                                      (DOLLARS IN THOUSANDS)
<S>                                                                             <C>        <C>          <C>
Cash, cash equivalents and short-term investments.............................  $ 136,812   $ 211,812    $ 394,094
                                                                                ---------  -----------  -----------
                                                                                ---------  -----------  -----------
Debt:
  Bank note (1)...............................................................  $     805   $     805    $     805
  13 1/2% senior discount notes due 2008......................................    157,465     157,465      157,465
                                                                                ---------  -----------  -----------
    Total debt................................................................    158,270     158,270      158,270
                                                                                ---------  -----------  -----------
Mandatorily redeemable common stock warrants..................................      6,567       6,567        6,567
                                                                                ---------  -----------  -----------
Stockholders' equity:
  Series A convertible preferred stock, $0.001 par value; 12,900,000 shares
    authorized actual and pro forma and no shares authorized pro forma as
    adjusted; 12,855,094 shares issued and outstanding actual and pro forma
    and no shares issued and outstanding pro forma as adjusted................         13          13       --
  Series B convertible preferred stock, $0.001 par value; 4,044,943 shares
    authorized actual and pro forma and no shares authorized pro forma as
    adjusted; 4,044,943 shares issued and outstanding actual and pro forma and
    no shares issued and outstanding pro forma as adjusted....................          4           4       --
  Series C convertible preferred stock, $0.001 par value; no shares authorized
    actual, 8,395,655 shares authorized pro forma and no shares authorized pro
    forma as adjusted; no shares issued and outstanding actual, 8,395,655
    shares issued and outstanding pro forma and no shares issued and
    outstanding pro forma as adjusted.........................................     --               8       --
  Series D convertible preferred stock, $0.001 par value; no shares authorized
    actual, 441,176 shares authorized pro forma and no shares authorized pro
    forma as adjusted; no shares issued and outstanding actual, 441,176 shares
    issued and outstanding pro forma and no shares issued and outstanding pro
    forma as adjusted.........................................................     --               1       --
  Common stock, $0.001 par value; 80,049,892 shares authorized actual,
    81,000,000 shares authorized pro forma and 250,000,000 shares authorized
    pro forma as adjusted; 8,042,530 shares issued actual and pro forma and
    68,493,581 shares issued pro forma as adjusted (2)........................          8           8           68
Treasury stock, at cost; 438,115 shares.......................................        (18)        (18)         (18)
Additional paid-in capital....................................................     37,212     102,841      285,089
Warrants......................................................................     --          10,371       10,371
Deferred compensation.........................................................     (5,210)     (5,210)      (5,210)
Accumulated deficit...........................................................    (38,756)    (38,756)     (38,756)
                                                                                ---------  -----------  -----------
    Total stockholders' equity (deficit)......................................     (6,747)     69,262      251,544
                                                                                ---------  -----------  -----------
      Total capitalization....................................................  $ 158,090   $ 234,099    $ 416,381
                                                                                ---------  -----------  -----------
                                                                                ---------  -----------  -----------
</TABLE>
 
- ------------------------------
(1) Consists of a $1.0 million note payable to Silicon Valley Bank which is
    being amortized over a 36-month period that ends in April 2001.
 
(2) Excludes 2,527,596 shares of common stock issued between January 1, 1999 and
    April 6, 1999 upon the exercise of options. Also excludes 7,184,674 shares
    of common stock issuable upon the exercise of outstanding warrants and
    3,649,130 shares of common stock issuable upon the exercise of outstanding
    options as of April 6, 1999.
 
                                       23
<PAGE>
                                    DILUTION
 
    Our pro forma net tangible book value at December 31, 1998 was $1.16 per
share. Pro forma net tangible book value per share represents the amount of our
total tangible assets less total liabilities, divided by the number of shares of
common stock outstanding after giving effect to the issuance of Series C
preferred stock to MCI WorldCom's investment fund and Microsoft, to the issuance
of Series C and Series D preferred stock to Qwest's subsidiary on April 6, 1999
and to the conversion of all outstanding shares of preferred stock into
51,076,051 shares of common stock upon the completion of this offering. Please
see "Capitalization." After giving effect to the sale of the 9,375,000 shares of
common stock in this offering, at a public offering price of $21.00 per share,
less underwriting discounts and commissions and other estimated expenses of this
offering, our as adjusted pro forma net tangible book value as of December 31,
1998 would have been $3.66 per share. This represents an immediate increase in
net tangible book value per share of $2.50 to existing stockholders and
immediate dilution in net tangible book value of $17.34 per share to new
investors in this offering. The following table illustrates the per share
dilution:
 
<TABLE>
<S>                                                            <C>        <C>
Public offering price per share..............................             $   21.00
  Pro forma net tangible book value per share at December 31,
    1998.....................................................  $    1.16
  Increase per share attributable to new investors...........       2.50
                                                               ---------
As adjusted pro forma net tangible book value per share after
  this offering..............................................                  3.66
                                                                          ---------
Dilution per share to new investors (1)......................             $   17.34
                                                                          ---------
                                                                          ---------
</TABLE>
 
- ------------------------
 
(1) If the underwriters' over-allotment option is exercised in full, dilution
    per share to new investors would be $17.02.
 
    The following table summarizes the number of shares of common stock
purchased from us, assuming conversion of all outstanding shares of preferred
stock into common stock, the total consideration paid and the average price per
share paid by the existing stockholders and by new investors in this offering,
before deduction of estimated underwriting discounts and commissions and other
expenses of this offering. The calculations in this table with respect to the
shares to be purchased by new investors in this offering reflect an initial
public offering price of $21.00 per share.
 
<TABLE>
<CAPTION>
                                                                  SHARES PURCHASED         TOTAL CONSIDERATION
                                                              -------------------------   ---------------------   AVERAGE PRICE
                                                                  NUMBER       PERCENT      AMOUNT     PERCENT      PER SHARE
                                                              --------------   --------   -----------  --------   -------------
<S>                                                           <C>              <C>        <C>          <C>        <C>
Existing stockholders.......................................      58,680,466     86.2%    $107,027,000   35.2%       $ 1.82
New investors...............................................       9,375,000     13.8     196,875,000    64.8        $21.00
                                                              --------------      ---     -----------     ---
    Total...................................................      68,055,466(1)    100%   $303,902,000    100%
                                                              --------------      ---     -----------     ---
                                                              --------------      ---     -----------     ---
</TABLE>
 
- ------------------------
 
(1) Excludes 2,527,596 shares of common stock issued between January 1, 1999 and
    April 6, 1999 upon the exercise of options. Also excludes 7,184,674 shares
    of common stock issuable upon the exercise of outstanding warrants and
    3,649,130 shares of common stock issuable upon the exercise of outstanding
    options as of April 6, 1999.
 
                                       24
<PAGE>
                      SELECTED CONSOLIDATED FINANCIAL DATA
 
    The following statement of operations data for the periods from our
inception on February 27, 1997 to December 31, 1997 and for the year ended
December 31, 1998, and the balance sheet data as of December 31, 1997 and 1998
(actual) have been derived from our consolidated financial statements and the
related notes to the financial statements. The following selected consolidated
financial data should be read in conjunction with our consolidated financial
statements and the related notes to the financial statements and "Management's
Discussion and Analysis of Financial Condition and Results of Operations"
included elsewhere in this prospectus.
 
<TABLE>
<CAPTION>
                                                                              FEBRUARY 27, 1997
                                                                               (INCEPTION) TO        YEAR ENDED
                                                                              DECEMBER 31, 1997   DECEMBER 31, 1998
                                                                             -------------------  -----------------
                                                                                 (DOLLARS IN THOUSANDS, EXCEPT
                                                                                        PER SHARE DATA)
<S>                                                                          <C>                  <C>
STATEMENT OF OPERATIONS DATA:
  Revenue..................................................................       $  --               $     528
  Operating expenses:
    Network and service costs..............................................          --                   4,695
    Selling, marketing, general and administrative.........................           2,534              23,153
    Depreciation and amortization..........................................               1               1,081
                                                                                    -------            --------
      Total operating expenses.............................................           2,535              28,929
                                                                                    -------            --------
  Loss from operations.....................................................          (2,535)            (28,401)
  Interest and other income (expense), net.................................             113              (7,933)
                                                                                    -------            --------
  Net loss.................................................................       $  (2,422)          $ (36,334)
                                                                                    -------            --------
                                                                                    -------            --------
  Net loss per share (basic and diluted)...................................       $   (1.12)          $  (12.18)
                                                                                    -------            --------
                                                                                    -------            --------
  Unaudited pro forma net loss per share (basic and diluted)(1)............                           $   (0.53)
                                                                                                       --------
                                                                                                       --------
OTHER FINANCIAL DATA:
  EBITDA (2)...............................................................       $  (2,342)          $ (26,628)
  Adjusted EBITDA (3)......................................................          (2,342)            (25,036)
  Net cash used for operating activities...................................          (1,560)            (19,024)
  Net cash used for investing activities...................................          (1,345)           (139,032)
  Net cash provided by financing activities................................          13,071             169,205
</TABLE>
 
<TABLE>
<CAPTION>
                                                                                    AS OF DECEMBER 31, 1998
                                                             AS OF         -----------------------------------------
                                                       DECEMBER 31, 1997    ACTUAL    PRO FORMA (4)  AS ADJUSTED (5)
                                                      -------------------  ---------  -------------  ---------------
                                                                          (DOLLARS IN THOUSANDS)
<S>                                                   <C>                  <C>        <C>            <C>
BALANCE SHEET DATA:
  Cash, cash equivalents and short-term
    investments.....................................       $  10,166       $ 136,812    $ 211,812       $ 394,094
  Equipment and furniture, net......................           1,621          11,510       11,510          11,510
  Total assets......................................          12,241         171,726      247,735         430,017
  Total debt........................................             568         158,270      158,270         158,270
  Mandatorily redeemable common stock warrants......          --               6,567        6,567           6,567
  Total stockholders' equity (deficit)..............          10,346          (6,747)      69,262         251,544
</TABLE>
 
- ------------------------------
 
(1) Unaudited pro forma net loss per share gives effect to conversion of the
    Series A, Series B, Series C and Series D preferred stock into common stock
    which will occur upon the closing of this offering.
 
(2) EBITDA consists of the net loss excluding net interest, depreciation and
    amortization of capital assets and deferred compensation expense. EBITDA is
    presented to enhance an understanding of our operating results and is not
    intended to represent cash flow or results of operations in accordance with
    generally accepted accounting principles for the period indicated and may be
    calculated differently than EBITDA for other companies.
 
(3) Total operating expenses for the year ended December 31, 1998 include
    $1,592,000 of operating lease expense to GATX Capital Corporation. No
    amounts were incurred to GATX for operating leases in 1997. Adjusted EBITDA
    reflects EBITDA excluding the GATX operating lease expense.
 
(4) Gives effect to the issuance of Series C preferred stock and warrants in
    March 1999 for $60 million, the issuance of Series C and Series D preferred
    stock and warrants in April 1999 for $15 million and the issuance of
    warrants in March and April 1999. Pro forma amounts are unaudited. See
    "Certain Relationships and Related Transactions--Series C Purchase
    Agreement; Other Agreements with MCI WorldCom and --Series C Purchase
    Agreement; Other Agreements with Microsoft and --Series C Purchase Agreement
    and Series D Purchase Agreement; Other Agreement with Qwest."
 
(5) Adjusts the pro forma information to give effect to this offering. As
    adjusted amounts are unaudited.
 
                                       25
<PAGE>
          MANAGEMENT'S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION
                           AND RESULTS OF OPERATIONS
 
OVERVIEW
 
    We are a leading service provider of high-speed local access networking
solutions using DSL technology to businesses. We began offering commercial
services in San Diego in April 1998, and have subsequently begun service in ten
additional markets: San Francisco, San Jose, Oakland/East Bay, Chicago, Los
Angeles, Orange County, Boston, Sacramento, New York and Philadelphia. We intend
to continue our network rollout into an additional 23 markets in 1999 and a
further 17 markets by the end of 2000.
 
    Since our inception in February 1997, our primary activities have consisted
of:
 
    - obtaining required governmental authorizations;
 
    - negotiating and executing interconnection agreements with incumbent
      carriers;
 
    - entering into strategic alliances;
 
    - identifying collocation space and locations for our Connection Points,
      Metro Service Centers and business offices;
 
    - acquiring and deploying equipment and facilities;
 
    - launching service trials;
 
    - hiring management and other personnel;
 
    - raising capital; and
 
    - developing and integrating our operations support system and other back
      office systems.
 
    We have incurred operating losses, net losses and negative operating cash
flow for each month since our formation. As of December 31, 1998, we had an
accumulated deficit of $38.8 million. We currently intend to substantially
increase our operating expenses and capital expenditures in an effort to rapidly
expand our infrastructure and network services. We expect to incur substantial
operating losses, net losses and negative cash flow during the network build-out
and initial penetration of each new market we enter. These losses are expected
to continue for at least the next several years.
 
    In March 1999, we entered into separate strategic arrangements with MCI
WorldCom and Microsoft. As part of our strategic arrangements, MCI WorldCom's
investment fund and Microsoft each invested $30 million in us. The MCI WorldCom
arrangement also designates us as MCI WorldCom's preferred provider of business
DSL lines in certain circumstances, and provides that MCI WorldCom is committed
to sell at least 100,000 of our DSL lines over a period of five years, subject
to penalties for failure to reach target commitments. In turn, we have
designated MCI WorldCom as our preferred provider of network services in certain
circumstances. In our Microsoft arrangement, we will jointly distribute with
Microsoft a co-branded DSL version of the Microsoft Network (MSN) service
focused on our small business customers and on our customers' teleworkers. In
April 1999, we entered into a customer relationship with Qwest Communications
Corporation, in connection with which Qwest's subsidiary, U.S. Telesource, Inc.,
invested $15 million in us.
 
    As a result of recent preferred stock and warrant issuances and stock option
grants, we anticipate that there will be significant charges to earnings in
future periods. These charges to earnings may total as high as $65 million over
the next several years.
 
                                       26
<PAGE>
FACTORS AFFECTING OPERATIONS
 
    REVENUE
 
    The following factors affect our revenue:
 
    - SERVICE OFFERING. We derive a majority of our operating revenue from DSL
      access and wide area network services. For both local access and wide area
      network connections, we bill our customers for monthly recurring charges
      based on the data transfer speeds selected by the customer. We offer flat
      rate plans for our services. In addition to monthly service fees, we bill
      users for nonrecurring service activation and installation charges. We
      also charge both monthly and nonrecurring charges to each customer for the
      high-speed connection between our Metro Service Center and the customer's
      router. To encourage potential customers to adopt our services, we
      sometimes offer reduced prices for an initial period of time. We expect
      that, as a result of competitive forces, our prices will decline over
      time.
 
    - PENETRATION OF TARGET MARKETS. We base our target market assessment on the
      number of local area networks in each market, which we believe is the best
      indication of data intensive business density and potential customers for
      our services. According to a leading data communications industry source,
      the total number of business local area networks in the United States is
      approximately 1.5 million, with an average of 40 users per local area
      network. We believe that our initial ten markets contain 23% of all local
      area networks in the United States. Our goal is to cover 60% of the local
      area networks in the United States, which we believe is achievable by
      building out a total of 50 markets. Initially, DSL is expected to reach
      over 70% of the businesses and residences served from the central offices.
      Within each metropolitan area, we expect to collocate in the appropriate
      number of central offices to cover 75% of the total market opportunity.
 
    - TURNOVER. To date, our customer turnover has been minimal. We expect this
      to increase in the future as competition intensifies.
 
    NETWORK AND SERVICE COSTS
 
    Our network and service costs are generally comprised of the following:
 
    - EQUIPMENT INSTALLATION CHARGES. In each market, we will require a number
      of field service technicians to install customer premise equipment at end
      user locations. We currently outsource most of this function.
 
    - MONTHLY RECURRING AND NONRECURRING LINE AND SERVICE CHARGES. We pay
      incumbent carriers a one-time installation and activation fee and a
      monthly service fee for each copper line.
 
    - METROPOLITAN AREA NETWORK TRANSPORT CHARGES. We incur charges for
      transport between our Connection Points and our Metro Service Centers.
      Currently, these charges are typically for DS-3 services from a
      competitive carrier or incumbent carrier. These charges also include
      customer connections to our network.
 
    - NETWORK FACILITIES OPERATING EXPENSES. We incur various recurring costs at
      our network locations. These costs include facility rent and utility
      costs.
 
    - WIDE AREA NETWORK CONNECTION CHARGES. We pay long distance carriers a
      one-time installation and activation fee and a monthly service fee for
      wide area network connections over a frame relay or Asynchronous Transfer
      Mode network. We are currently leasing these services from long distance
      carriers.
 
    - COST OF CUSTOMER PREMISE EQUIPMENT. As part of our DSL product offering,
      we provide the customer premise equipment and expense the cost of the
      customer premise equipment for each customer line.
 
                                       27
<PAGE>
    - EQUIPMENT OPERATING LEASE EXPENSES. We currently take advantage of
      short-term operating leases to finance the acquisition of substantially
      all of our network equipment, including DSL multiplexers, Asynchronous
      Transfer Mode switches and routers. We may decide to purchase and to
      capitalize some or all of this equipment in the future.
 
    - LINE REPAIR AND SUPPORT COSTS. Similar to other telecommunications
      providers, we estimate that a small percentage of our lines may require
      repair or support. These costs will consist of field dispatch labor and a
      portion of our Network Operations Center costs.
 
    SELLING, GENERAL AND ADMINISTRATIVE COSTS
 
    Our selling, general and administrative expenses include customer service
and technical support, information systems, billing and collections, general
management and overhead, and administrative functions. Headcount in functional
areas, such as customer service, engineering and operations, will increase as we
expand our network, and if our number of customers increases.
 
    - SALES AND MARKETING COSTS. Our sales and marketing efforts focus on
      attracting and retaining service providers, including national and
      regional Internet Service Providers, national and regional systems and
      network integrators, value-added resellers, competitive carriers and long
      distance carriers, as well as large business customers.
 
    - GENERAL AND ADMINISTRATIVE COSTS. As we expand our network, we expect the
      number of employees located in specific markets to grow. Certain
      functions, such as customer service, network operations, finance, billing
      and site planning, are likely to remain centralized in order to achieve
      economies of scale.
 
    DEPRECIATION AND AMORTIZATION
 
    Depreciation expense arising from our network equipment will be minimal
since leased equipment expenses will reflect most of the cost and financing of
this equipment. Collocation fees are capitalized and amortized over an estimated
useful life of ten years.
 
RESULTS OF OPERATIONS
 
    REVENUE
 
    We did not offer commercial services in 1997 and, as a result, did not
record any revenue in 1997. During the year ended December 31, 1998, we
continued the development of our business operations, commencing service in the
San Diego market in April, the San Francisco, the Oakland/East Bay and San Jose
markets in July, the Los Angeles and Orange County markets in September and the
Chicago market in October. We recorded revenue of $528,000 during this period,
which was primarily from DSL service and installation charges, net of discounts
given to customers.
 
    NETWORK AND SERVICE COSTS
 
    Since we did not offer commercial services in 1997, we did not record any
network or service costs in 1997. For the year ended December 31, 1998, we
recorded network and service costs of $4.7 million. We expect network and
service costs to increase significantly in future periods as we expand our
network into additional markets.
 
    SELLING, MARKETING, GENERAL AND ADMINISTRATIVE
 
    From inception through December 31, 1997 selling, marketing, general and
administrative expenses were $2.5 million and consisted primarily of salaries
and legal and consulting fees incurred to establish a management team and
develop our business. For the year ended December 31, 1998, we recorded selling,
marketing, general and administrative expenses of $23.2 million. This increase
is attributable to a continued increase in staffing levels, increased marketing
efforts coinciding with the launch of
 
                                       28
<PAGE>
commercial services and increased legal fees associated with the development of
additional markets. We expect selling, marketing, general and administrative
expenses to continue to increase significantly as we expand our business.
 
    DEPRECIATION AND AMORTIZATION
 
    Depreciation from network equipment is minimal since substantially all of
this equipment is currently leased. Depreciation and amortization was $1,000 for
the period from inception through December 31, 1997 and was $1.1 million for the
year ended December 31, 1998. The increase was due to the commencement of our
operations in 1998. We expect depreciation and amortization to increase
significantly in future periods as we increase capital expenditures to expand
our network.
 
    OTHER INCOME AND EXPENSE
 
    Other income and expense consists primarily of interest income from our cash
and short-term investments and interest expense associated with our debt. From
inception through December 31, 1997 net interest income was $113,000, which was
primarily attributable to the interest income earned from the proceeds raised in
our Series A preferred stock financing. For the year ended December 31, 1998, we
recorded net interest expense of $8.0 million, consisting of interest income of
$5.8 million generated from invested cash balances, offset by $13.8 million in
interest expense. The increase in the interest expense is substantially due to
the accretion of interest on the senior discount notes that were issued in May
1998.
 
    INCOME TAXES
 
    We generated net operating loss carryforwards of $2.1 million from inception
to December 31, 1997 and $35.0 million during the year ended December 31, 1998.
We expect significant consolidated losses for the foreseeable future which will
generate additional net operating loss carryforwards. However, our ability to
use net operating losses may be subject to annual limitations. In addition,
income taxes may be payable during this time due to operating income in certain
tax jurisdictions. In the future, if we achieve operating profits and the net
operating losses have been exhausted or have expired, we may experience
significant tax expense. We recognized no provision for taxes because we
operated at a loss throughout 1997 and 1998.
 
LIQUIDITY AND CAPITAL RESOURCES
 
    The development and expansion of our business requires significant capital
expenditures. The principal capital expenditures incurred during the build-out
phase of any market involve the procurement, design and construction of our
Connection Points, one or two Metro Service Centers and other elements of our
network design.
 
    The number of targeted central offices in a market varies, as does the
average capital cost to build our Connection Points in a given market. Capital
expenditures, including payments for collocation fees, were $23.5 million for
the year ended December 31, 1998. We expect our capital expenditures to be
substantially higher in future periods, arising primarily from payment of
collocation fees and the purchase of infrastructure equipment necessary for the
development and expansion of our network.
 
    Through December 31, 1998, we financed our operations primarily through
private placements of equity totaling $30.8 million, of which we received $30.3
million from our venture capital and institutional sponsors, the use of
operating equipment leases totaling $26.5 million, borrowings under a note
payable from Silicon Valley Bank of $1.0 million, and $144.0 million in net
proceeds raised from the issuance of the senior discount notes. As of December
31, 1998, we had an accumulated deficit of $38.8 million and cash, cash
equivalents and short-term investments of $136.8 million. In March 1999, we
received $60.0 million in separate investments by Microsoft and MCI WorldCom's
investment fund. In April 1999, we received $15.0 million in an equity
investment by Qwest's subsidiary.
 
                                       29
<PAGE>
    For the year ended December 31, 1998, the net cash used in our operating
activities was $19.0 million. This cash was used for a variety of operating
purposes, including salaries, consulting and legal expenses, network operations
and overhead expense. Our net cash used for investing activities for the year
ended December 31, 1998 was $139.0 million and was used primarily for purchases
of short-term investments and equipment and payments of collocation fees. Net
cash provided by financing activities for the year ended December 31, 1998 was
$169.2 million and primarily came from the issuance of the senior discount notes
and from the issuance of preferred stock.
 
    We believe that the net proceeds from this offering, together with our
existing cash and short-term investments, existing and anticipated equipment
lease financings and future revenue generated from operations, will be
sufficient to fund our operating losses, capital expenditures, lease payments
and working capital requirements through June 2000. We expect our operating
losses and capital expenditures to increase substantially primarily due to our
network expansion. We expect that additional financing will be required in the
future. We may attempt to raise financing through some combination of commercial
bank borrowings, leasing, vendor financing or the private or public sale of
equity or debt securities. In March 1999, we entered into 36-month lease lines
with GATX Capital Corporation for an aggregate of up to $24 million in equipment
lease financing. We have also received a financing proposal from GATX for up to
$10 million of additional lease financing to be used for collocation fees. In
April 1999, we entered into a lease agreement with Cisco Systems Capital
Corporation for an aggregate of up to $20 million in equipment lease financing.
Our senior discount notes contain covenants that restrict the our ability to
make certain payments, including dividend payments, and incur additional debt.
See "Dividend Policy."
 
    Our capital requirements may vary based upon the timing and success of our
rollout and as a result of regulatory, technological and competitive
developments or if
 
    - demand for our services or our anticipated cash flow from operations is
      less or more than expected;
 
    - our development plans or projections change or prove to be inaccurate;
 
    - we engage in any acquisitions; or
 
    - we accelerate deployment of our network services or otherwise alter the
      schedule or targets of our rollout plan.
 
    Equity or debt financing may not be available to us on favorable terms or at
all. See "Risk Factors--We will need significant additional funds, which we may
not be able to obtain."
 
IMPACT OF THE YEAR 2000 ISSUE
 
    Many computer programs have been written using two digits rather than four
to define the applicable year. This poses a problem at the end of the century
because these computer programs may recognize a date using "00" as the year 1900
rather than the year 2000. This, in turn, could result in major system failures
or miscalculations, and is generally referred to as the "Year 2000 issue." We
have formulated and, to a large extent, effected a plan to address our Year 2000
issues.
 
    Our Year 2000 plan applies to two areas: internal business systems and
compliance by external customers and providers. We have completed our Year 2000
compliance testing for all of our internal systems and believe that they are
Year 2000 compliant. Because we are a young company, we believe we have been
able to build our business systems with the Year 2000 issue in mind in a more
effective manner than many older companies. Therefore, there have been few Year
2000 changes required to our existing systems and applications. We have
substantially completed a compliance check of our external customers and
providers, except for the incumbent carriers. Based on responses from these
third parties, other than the incumbent carriers, we believe that they will not
experience Year 2000 problems that would materially and adversely affect our
business. We have not been able to conduct a compliance check of incumbent
carriers nor assess the incumbent carriers' Year 2000 compliance. To
 
                                       30
<PAGE>
the extent that one or more incumbent carriers or other third parties experience
Year 2000 problems, our network and services could be adversely affected.
Furthermore, the purchasing patterns of our customers may be affected by Year
2000 issues as companies expend significant resources to correct their current
systems for Year 2000 compliance. These expenditures may result in reduced funds
available for our services. Any of these developments could have a material and
adverse effect on our business, prospects, operating results and financial
condition. We have not fully determined the risks associated with the reasonably
worst-case scenario and have not formulated a contingency plan to address Year
2000 issues. We do not expect to have a specific contingency plan in place in
the future.
 
FINANCIAL INFORMATION
 
    The preceding discussion and analysis is based on our consolidated financial
statements and the related notes and should be read in conjunction with the
consolidated financial statements and the related notes included in this
prospectus.
 
FORWARD-LOOKING STATEMENTS
 
    This prospectus includes forward-looking statements. These forward-looking
statements address, among other things:
 
    - our network rollout plans and strategies;
 
    - development and management of our business;
 
    - our ability to attract, retain and motivate qualified personnel;
 
    - success of our strategic alliances;
 
    - our ability to attract and retain customers;
 
    - the extent of acceptance of our services;
 
    - the market opportunity and trends in the markets for our services;
 
    - our ability to upgrade our technologies;
 
    - prices of telecommunication services;
 
    - the nature of regulatory requirements that apply to us;
 
    - our ability to obtain any required governmental authorizations;
 
    - our future capital expenditures and needs;
 
    - our ability to obtain financing on commercially reasonable terms;
 
    - our ability to implement a Year 2000 readiness program;
 
    - our ability to compete; and
 
    - the extent and nature of competition.
 
    These statements may be found in this section, in the front inside cover of
this prospectus, in the sections of this prospectus entitled "Summary," "Risk
Factors," "Use of Proceeds" and "Business" and in this prospectus generally.
 
    We have based these forward-looking statements on our current expectations
and projections about future events. However, our actual results could differ
materially from those anticipated in these forward-looking statements as a
result of risks facing us, including risks stated in "Risk Factors," or faulty
assumptions on our part. For example, assumptions that could cause actual
results to vary materially from future results include, but are not limited to:
 
    - our ability to successfully market our services to current and new
      customers;
 
    - our ability to generate customer demand for our services in our target
      markets;
 
                                       31
<PAGE>
    - the development of our target market and market opportunities;
 
    - market pricing for our services and for competing services;
 
    - the extent of increasing competition;
 
    - our ability to acquire funds to expand our network;
 
    - the ability of our equipment and service suppliers to meet our needs;
 
    - trends in regulatory, legislative and judicial developments;
 
    - our ability to manage growth of our operations; and
 
    - our ability to access regions and enter into suitable interconnection
      agreements with incumbent carriers.
 
    We undertake no obligation to publicly update or revise any forward-looking
statements, whether as a result of new information, future events or otherwise.
In light of these risks, uncertainties and assumptions, the forward-looking
events discussed in this prospectus might not occur.
 
                      DESCRIPTION OF CERTAIN INDEBTEDNESS
 
    In November 1997 and May 1998, we entered into 36-month lease lines for an
aggregate $26.5 million in lease financing with Sun Financial Group, Inc., now
GATX Capital Corporation, pursuant to which we lease office equipment,
telecommunications equipment, network equipment and furniture on an operating
lease basis. In connection with this leasing arrangement, we issued to GATX a
warrant to purchase 574,380 shares of common stock at a price of $1.85 per
share. This warrant is immediately exercisable. In March 1999, we entered into
additional 36-month lease lines for an aggregate of up to $24 million in lease
financing with GATX to be used for equipment. In connection with these March
1999 leases, we issued GATX warrants to purchase an aggregate of 45,498 shares
of common stock at a price of $10.55 per share. These warrants are immediately
exercisable. We also received a financing proposal from GATX in February 1999
for up to $10 million in additional lease financing to be allocated for
collocation fees. In April 1999, we entered into an agreement with Cisco Systems
Capital Corporation for up to $20 million in equipment lease financing and
issued to Cisco a warrant to purchase up to 75,000 shares of common stock at an
exercise price per share of $10.55. This warrant is immediately exercisable.
 
    We also have outstanding senior discount notes, which we issued in May 1998.
These 13 1/2% notes were issued at a discount and raised net proceeds of
approximately $144.0 million. These notes are senior unsecured obligations that
mature with a principal amount of $290 million on May 15, 2008. The discount
amount is being accreted to interest expense for the first five years of the
notes; cash interest on these notes will not accrue prior to May 15, 2003, but
will do so after that date and will be payable semi-annually each year,
commencing November 15, 2003. These notes are redeemable at our option, in whole
or in part, at any time after May 15, 2003 and, prior to May 15, 2001, out of
the proceeds of certain equity offerings, at predetermined redemption prices
together with accrued and unpaid interest through the date of redemption. We
will not use the proceeds of this offering to redeem any of these notes. Upon a
change of control, each holder of these notes may require us to repurchase the
notes at 101% of the principal amount thereof, plus accrued and unpaid interest
to the date of purchase. These notes contain certain restrictive covenants,
including limitations on future indebtedness, restricted payments, transactions
with affiliates, liens, sale of stock of subsidiaries, dividends, mergers and
transfers of assets.
 
                                       32
<PAGE>
                                    BUSINESS
 
THE COMPANY
 
    We are a leading service provider of high-speed local access networking
solutions using DSL technology to businesses. We have designed our network to
give our customers a high-speed "always on" local connection to the Internet and
to private local and wide area networks. We offer a variety of DSL technologies
that deliver data transfer rates ranging from 128 Kbps to 7.1 Mbps. For
customers that subscribe at the 7.1 Mbps rate, our network provides transfer
speeds faster than frame relay and T-1 circuits, and is approximately 125 times
the speed of the fastest dial-up modem and over 55 times the speed of integrated
services digital network (ISDN) lines. Through our packet-based network,
multiple users on a single connection are able to simultaneously access the
Internet and private networks. Beyond high-speed access, we also offer a growing
suite of features and applications that we can individually configure to each
user's needs. We believe our network solutions will increase remote office and
worker productivity and reduce the complexity of communications for businesses.
 
    Since our inception in February 1997, we have made substantial progress in
implementing a scalable nationwide network. We began offering commercial
services in San Diego in April 1998, and have subsequently begun service in ten
additional markets: San Francisco, San Jose, Oakland/East Bay, Chicago, Los
Angeles, Orange County, Boston, Sacramento, New York and Philadelphia. We intend
to continue our network rollout into an additional 23 markets in 1999 and a
further 17 markets by the end of 2000. Upon completion of this network
expansion, we anticipate providing services in 50 of the nation's largest
metropolitan areas, which we believe contain 60% of the nation's local area
networks. We have signed interconnection agreements with Ameritech, Bell
Atlantic, BellSouth, GTE, Pacific Bell and U S WEST, and we are currently
pursuing interconnection arrangements with two other incumbent carriers. As of
January 31, 1999, we provide service or have installed equipment in nearly 200
incumbent carrier central offices. We have obtained competitive carrier
authority or have been permitted to operate as a competitive carrier in 21
states.
 
    In March 1999, we entered into separate strategic arrangements with MCI
WorldCom and Microsoft. As part of our strategic arrangements, MCI WorldCom's
investment fund and Microsoft each invested $30 million in us. The MCI WorldCom
arrangement also designates us as MCI WorldCom's preferred provider of business
DSL lines in certain circumstances, and provides that MCI WorldCom is committed
to sell at least 100,000 of our DSL lines over a period of five years, subject
to penalties for failure to reach target commitments. In turn, we have
designated MCI WorldCom as our preferred provider of network services in certain
circumstances. MCI WorldCom will also work with us to develop voice and data
applications over a single DSL connection. In our Microsoft arrangement, we will
jointly distribute with Microsoft a co-branded DSL version of the Microsoft
Network (MSN) service focused on our small business customers and on our
customers' teleworkers. In April 1999, we entered into a customer relationship
with Qwest Communications Corporation, in connection with which Qwest's wholly
owned subsidiary, U.S. Telesource, Inc., invested $15 million in us.
 
    We also market our services through our direct sales force and through our
partnerships with recognized leaders in the networking industry, including
Microsoft and Cisco. Under our strategic partnership with Cisco, Cisco agreed to
jointly market and sell our networking solutions to its customer base and will
engage in joint development projects with us. As of January 31, 1999, we had
over 650 lines in service, and we are currently under contract to supply over
9,000 additional DSL lines to our business and service provider customers,
including Cisco, Silicon Graphics, Inc., QUALCOMM Incorporated, Wind River
Systems and Broadcom Corporation.
 
    Our senior management team has extensive experience in developing
next-generation networking businesses. Our President and Chief Executive
Officer, Catherine Hapka, was previously the founder, President and Chief
Operating Officer of !NTERPRISE Networking Services, U S WEST's data networking
business. Scott Chandler, our Chief Financial Officer, was previously President
and Chief
 
                                       33
<PAGE>
Executive Officer of C-COR Electronics, Inc., a manufacturer of broadband
telecommunications equipment. James Greenberg, our Chief Network Officer,
directed the design, planning, operation and construction of Sprint
Corporation's data networks. Frank Tolve, our Chief Sales Officer, previously
served as Vice President, Sales Operations of Bay Networks. Our sponsors, which
include Microsoft, MCI WorldCom's investment fund, Qwest's subsidiary, Kleiner
Perkins Caufield & Byers, Enterprise Partners, Brentwood Venture Capital, the
Sprout Group and a subsidiary of Enron Corp., have to date invested
approximately $105.3 million.
 
MARKET OPPORTUNITY
 
    We believe that a substantial market opportunity exists as a result of the
convergence of six factors:
 
    - the growing demand for high-speed access to the Internet and corporate
      networks;
 
    - the inherent limitations of dial-up modems as a connection to data
      networks;
 
    - the need for large companies to improve the productivity of their remote
      offices and workers;
 
    - the need for small and medium businesses to have an integrated
      communication solution for their networking requirements;
 
    - the increasing adoption of DSL and widespread use of packet-based
      networks; and
 
    - the 1996 Telecommunications Act.
 
    GROWING DEMAND FOR HIGH-SPEED ACCESS TO THE INTERNET AND CORPORATE NETWORKS
 
    The value of goods and services sold through the Internet will grow from
$2.6 billion in 1996 to $400 billion in 2002, according to analyst projections.
Today, business spending for connecting remote workers, branch offices and
corporate headquarters to each other and to customers, suppliers and partners --
either through the Internet or private networks -- is large and growing.
Industry analysts estimate that the U.S. market for remote Internet and local
area network access will grow from $5.9 billion in 1997 to $11.7 billion by
2002. Industry sources estimate that spending in the United States on
distributed networking and network services and applications will grow from
$54.2 billion in 1998 to $173 billion in 2002. Much of that growth is expected
to result from increased demand for e-mail, Web hosting services, e-commerce,
collaboration and real-time video services and applications. Industry sources
expect spending on distributed networking and network services and applications
to encompass 57% of a company's total annual information technology spending by
2002.
 
    LIMITATIONS OF DIAL-UP MODEMS AND INTEGRATED SERVICES DIGITAL NETWORK (ISDN)
 
    Because only five percent of buildings in the United States are currently
connected to high-speed fiber rings -- typically large buildings in metropolitan
areas or clusters of buildings in regional campus parks -- the vast majority of
workers who access data networks do so through slow dial-up modems connected to
the traditional circuit switched public telephone system. These traditional
dial-up modems are creating a bottleneck in data communications because the
data-carrying capacity of the fastest commercially available dial-up modem is
only 56 Kbps. The capacity of another alternative, an integrated services
digital network (ISDN) line, is only 128 Kbps. While integrated services digital
network (ISDN) technology provides improved capacity relative to dial-up modems,
the cost of an integrated services digital network (ISDN) solution is often
prohibitive.
 
    NEEDS OF LARGE BUSINESSES FOR REMOTE OFFICE AND WORKER PRODUCTIVITY
 
    Many large companies are supporting increasing numbers of remote offices and
workers. These companies face the challenge of finding a cost effective way to
make their remote workers as
 
                                       34
<PAGE>
productive as those who have access to all of the high performance
communications and networking resources available to workers located at
corporate headquarters. A high-speed network solution that encompasses access to
the corporate local area network, the corporate telephone system, the Internet,
the corporate video conferencing system, customers, suppliers and partners would
substantially increase remote office and worker productivity. At present, large
businesses are incurring significant capital expenditures to purchase equipment
to support dial-up modems and integrated services digital network (ISDN)
connections, and paying for high cost technical support personnel only to
implement networking solutions that fail to optimize worker productivity.
 
    NEEDS OF SMALL AND MEDIUM BUSINESSES FOR INTEGRATED COMMUNICATION SOLUTIONS
 
    A significant number of small and medium businesses have no practical
alternative to dial-up modems or integrated services digital network (ISDN) for
their workers to access the Internet and remote local area networks. As a
result, these workers suffer productivity limitations associated with slow
transmission speeds. In addition, these businesses need to contend with the cost
and complexity of retaining multiple vendors for their communication needs:
incumbent carriers for local voice traffic; long distance carriers for long
distance voice traffic; Internet Service Providers for Internet access; and
equipment integrators for on-premises voice and network systems. We believe that
these businesses can benefit from working with a single service provider that
offers integrated communication solutions, using a single connection.
 
    EMERGENCE OF DSL AND PACKET-BASED TECHNOLOGIES
 
    DSL technology dramatically increases the data, voice and video carrying
capacity of standard copper telephone lines. Because DSL technology uses
existing copper telephone lines, a broad network deployment can be implemented
rapidly, and requires a lower initial fixed investment than some existing
alternative technologies, such as fiber, cable modems and satellite
communications systems. A significant portion of the build-out of a DSL-based
network is directly related to the demand of paying subscribers, resulting in a
success-based deployment of capital.
 
    Packet-based networks often are more efficient than traditional
point-to-point networks, and allow end users to connect to any location that can
be assigned an Internet Protocol address. Traditional point-to-point networks,
including the traditional telephone network and private line networks, are less
efficient because they require a dedicated connection between two locations.
Packet-based networks allow multiple users to share connections between
locations.
 
    1996 TELECOMMUNICATIONS ACT
 
    The 1996 Telecommunications Act allows competitive carriers to leverage the
existing incumbent carrier infrastructure, as opposed to building a competing
infrastructure at significant cost. The 1996 Telecommunications Act requires all
incumbent carriers to allow competitive carriers to collocate their equipment
along with incumbent carrier equipment in incumbent carrier central offices,
which enables competitive carriers to access end users through existing
telephone line connections. The 1996 Telecommunications Act creates an incentive
for incumbent carriers that were formerly part of the Bell system to cooperate
with competitive carriers: these incumbent carriers cannot provide long distance
service until regulators determine that there is competition in the incumbent
carrier's local market.
 
    MARKET IMPACT OF CONVERGENCE
 
    We believe the convergence of these factors has had several fundamental
effects on the communications market. New carriers can:
 
    - leverage the existing network infrastructure by obtaining local network
      access connections, and offer efficient high-speed data, voice and video
      networks;
 
                                       35
<PAGE>
    - provide large businesses with productivity enhancing remote office and
      worker networking solutions;
 
    - offer small and medium businesses integrated voice and data solutions that
      reduce the complexity of using multiple vendors for communication
      services; and
 
    - build new networks that can provide efficient high-speed access over a
      single connection to any Internet Protocol address on the Internet and/or
      corporate network, along with features and applications that can be
      configured to meet each user's needs.
 
THE RHYTHMS SOLUTIONS
 
    We believe our network solutions effectively address many of the unmet
communications needs of today's businesses by offering an appealing combination
of quality, performance, price and service. Our network consists of:
 
    - HIGH-SPEED, "ALWAYS ON" LOCAL CONNECTIONS.  Our network delivers
      high-speed, "always on" local access. Using DSL technology over standard
      copper telephone lines, our network is capable of delivering data transfer
      rates at speeds ranging from 128 Kbps to 7.1 Mbps. For customers that
      subscribe at the 7.1 Mbps rate, the transfer rate is faster than frame
      relay and T-1 circuits, and is approximately 125 times the rate of the
      fastest dial-up modem and over 55 times the rate of an integrated services
      digital network (ISDN) line. Moreover, unlike dial-up modems and
      integrated services digital network (ISDN) lines, the DSL solution is
      "always-on" -- it does not require users to dial-up to connect to the
      Internet or their local area network for each use.
 
    - METROPOLITAN AND WIDE AREA OVERLAY NETWORK.  We have designed our network
      so that we can effectively and efficiently manage data traffic within and
      among the metropolitan areas in which we offer our services. We use
      transport services provided by other carriers for local access to users,
      metropolitan area network connections and for long distance backbone
      capacity. This overlay network is designed to route and switch traffic
      within each metropolitan area, keeping local traffic local and sending
      only long distance traffic over the wide area network, thereby increasing
      overall network capacity and reliability and minimizing our backbone
      costs. We manage the network and monitor service levels on a nationwide
      basis from our Network Operations Center in Denver.
 
    - PRODUCTIVITY ENHANCING FEATURES AND APPLICATIONS.  We offer a growing
      suite of network-enabled features and applications that extend the
      functionality of corporate communications and networking resources to
      remote offices and workers. We also offer remote offices and workers, as
      well as small and medium businesses high performance Internet access
      solutions in conjunction with our service provider customers.
 
    - SERVICE FLEXIBILITY.  We have designed our network so that we are able,
      over a single DSL connection, to individually configure each network
      user's features and applications.
 
    - TURNKEY SOLUTION.  We offer turnkey network solutions for our customers by
      providing each customer with a single point of contact for a complete
      package of services, including network implementation, maintenance,
      billing and the DSL modem. For large customers, we provide complete
      project management, including design, implementation and results
      reporting. In some cases, we also seamlessly link our network operations
      systems to existing customer information systems to ensure maximum service
      efficiency.
 
                                       36
<PAGE>
BUSINESS STRATEGY
 
    Our goal is to become the leading national service provider of high
performance networking solutions for remote offices and workers. We intend to
implement the following strategies to achieve our goal:
 
    EXPLOIT EARLY MOVER ADVANTAGE
 
    We intend to exploit our early market entrance to deploy our network and
establish strong relationships with business and service provider customers. As
of January 31, 1999, we provide service or had installed our network equipment
in nearly 200 central offices. Installation on this scale requires significant
time and resources; therefore, we believe our progress to date provides us a
significant time-to-market advantage over would-be competitors. We have gained
significant build-out experience, which we believe will streamline our further
expansion. We plan to construct our network rapidly so that we are an early
mover in our other target markets. We intend to exploit our early mover
advantage to gain significant market share in our target markets.
 
    FOCUS ON PERFORMANCE-DRIVEN BUSINESS CUSTOMERS
 
    We believe that the underserved segment of the business networking market
that demands high performance is currently relying on dial-up modems or
integrated services digital network (ISDN) for network access. Many large
businesses have remote offices and workers that are not able to take advantage
of the full array of communications and networking resources available to
workers at the main office. In addition to offering these businesses high-speed
access to the Internet and corporate networks, we intend to offer them
network-enabled features and applications that increase worker productivity.
Further, we believe that small and medium businesses are looking for an
integrated service provider to reduce their reliance on multiple vendors.
Accordingly, we intend to offer multiple networking services, including voice
and data services over a single DSL connection, to meet the needs of small and
medium businesses.
 
    EXPAND NETWORK-ENABLED FEATURES AND APPLICATIONS
 
    We seek to have our network become a platform that facilitates the delivery
of productivity-enhancing features and applications to businesses and their
employees. By collaborating with industry leaders such as MCI WorldCom,
Microsoft and Cisco, we intend to jointly develop features and applications that
will meet the needs of our customers. For example, as part of our strategic
agreement with MCI WorldCom, we have agreed to jointly develop voice and data
applications over a single DSL connection. In addition, we believe that the
proliferation of high-speed local access networks, such as our own, will
encourage third parties to create more bandwidth-intensive features and
applications. One of our objectives in providing these enhanced features and
applications is to strengthen customer loyalty and increase revenue per network
user.
 
    ESTABLISH STRONG DISTRIBUTION CHANNELS
 
    We intend to build strong distribution channels. For large businesses, we
are building a direct sales force and are entering into strategic joint
marketing alliances. We have entered into a strategic alliance with Microsoft in
which we will jointly distribute with Microsoft a co-branded DSL version of the
Microsoft Network service focused on our small business customers and our
customers' teleworkers. We have also entered into a strategic alliance with MCI
WorldCom in which we have been designated its preferred provider of business DSL
connections for large, medium and small businesses. In addition, we entered into
a strategic alliance with Cisco, in which we will jointly market and sell our
networking solutions to large businesses. For small and medium businesses, we
will distribute our services through our service provider customers. Over time,
we will seek to develop additional strategic alliances,
 
                                       37
<PAGE>
focusing on partners that can both add value to our network and give us a
meaningful distribution channel.
 
    PROVIDE SUPERIOR CUSTOMER SERVICE
 
    As part of our strategy to obtain and retain business and service provider
customers, we intend to provide superior service and customer care. We will
guarantee high-quality service by providing carrier-class networking solutions
and superior customer service. Our carrier-class networking solutions include
end-to-end proactive network monitoring and management through our Network
Operations Center, 24 hours a day, seven days a week. We also offer multiple
security features and a network that we can scale to meet demand. Our customer
service includes a personal and Web-based single point of contact, a complete
packaged solution including the DSL modem, installation, activation and network
management, and specific customer service objectives against which we measure
our performance. Our objective in providing outstanding customer service is to
provide a high level of customer satisfaction, achieve customer loyalty and
accelerate the adoption rate of our service.
 
STRATEGIC PARTNERSHIPS
 
    MCI WORLDCOM
 
    In March 1999, we entered into a strategic partnership with MCI WorldCom,
which was amended in April 1999, pursuant to which, among other things:
 
    - MCI WORLDCOM INVESTMENT. MCI WorldCom's investment fund invested $30
      million in us, in return for 3,731,410 shares of our Series C preferred
      stock, which are convertible into 4,477,692 shares of common stock, and a
      warrant to purchase 720,000 shares of our common stock at $6.70 per share.
      MCI WorldCom's investment fund also received a warrant to purchase 136,996
      shares of common stock at the per share purchase price equal to the price
      per share paid in this offering.
 
    - PROVIDING DSL TO MCI WORLDCOM. We have been designated MCI WorldCom's
     preferred provider of business DSL access services in areas where we deploy
     our network, except for services to certain subsidiaries and in locations
     where MCI WorldCom deploys its own DSL equipment. We have a right of first
     refusal to match offers made to MCI WorldCom by other providers of DSL
     services.
 
     MCI WorldCom has committed to sell a minimum of 100,000 business quality
     DSL lines, subject to penalties for failure to reach target commitments.
     MCI WorldCom will have 60 months to place orders for these lines, starting
     on the date when we have 1,250 collocations in commercial service in at
     least 29 metropolitan statistical areas. As part of our agreement, we must
     provide specified service levels and have available capacity.
 
    - OBTAINING NETWORK SERVICES FROM MCI WORLDCOM. We have designated MCI
      WorldCom as our preferred provider of network services, including
      metropolitan area network services, long-haul backbone services and
      Internet Protocol backbone services. MCI WorldCom has a right of first
      refusal to provide all of these services to us.
 
    - COLLABORATION. We will jointly develop voice and data applications over a
      single DSL connection. We will also form a working group with MCI WorldCom
      to develop and implement the systems and procedures necessary to jointly
      deploy DSL service nationwide. We will collaborate with MCI WorldCom in
      selecting technologies and vendors to support our network deployments.
 
    MICROSOFT
 
    In March 1999, we entered into a strategic partnership with Microsoft,
pursuant to which, among other things:
 
                                       38
<PAGE>
    - MICROSOFT INVESTMENT. Microsoft invested $30 million in us, in return for
      3,731,409 shares of our Series C preferred stock, which are convertible
      into 4,477,691 shares of common stock, and a warrant to purchase 720,000
      shares of our common stock at $6.70 per share.
 
    - CO-BRANDING FOR SMALL BUSINESSES AND TELEWORKERS. Microsoft has agreed to
      jointly distribute with us over the Internet a co-branded DSL version of
      the Microsoft Network service focused on our small business customers and
      on our customers' teleworkers. This agreement expires in March 2002.
 
    QWEST
 
    In April 1999, we entered into a customer relationship with Qwest, in
connection with which Qwest's wholly owned subsidiary, U.S. Telesource, Inc.,
invested $15 million in us, in return for 932,836 shares of Series C preferred
stock, which are convertible into 1,119,403 shares of common stock, and 441,176
shares of Series D preferred stock, which are convertible into 441,176 shares of
common stock, subject to adjustment if the purchase price per share in this
offering is less than $17.00. U.S Telesource also received a warrant to purchase
180,000 shares of our common stock at $6.70 per share.
 
    CISCO SYSTEMS
 
    In October 1998, we entered into a strategic partnership with Cisco, in
which Cisco agreed to work jointly with us to sell our services to its customers
including providing compensation to its sales representatives for selling our
services. In addition, Cisco has committed to a joint marketing program with us
to increase our market recognition among businesses. We are also under contract
with Cisco to manage and upgrade its remote access program for 8,500 teleworkers
nationwide.
 
RHYTHMS NETWORK SERVICES, FEATURES AND APPLICATIONS
 
    We offer our customers solutions that address many of their high performance
networking needs. Our local connection services use a variety of DSL
technologies to deliver high-speed, "always on" local access. We also aggregate
traffic within metropolitan areas and route or switch the traffic to our service
provider customers, or to a corporate local area network within the same
metropolitan area or another metropolitan area using our inter-network
connections. In addition to local connections and metropolitan and wide area
inter-network connections, we offer a growing suite of network-enabled features
and applications.
 
    LOCAL CONNECTIONS
 
    Our local connection services connect individual users or multiple users on
a local area network to our metropolitan or national network or to the Internet
using DSL technology over traditional telephone lines. Using DSL technology over
copper lines, our network is capable of data transfer rates ranging from 128
Kbps to 7.1 Mbps. Unlike dial-up modems and integrated services digital network
(ISDN) lines, the DSL solution is "always on" -- it does not require users to
dial-up to connect to the Internet or their local area network for each use.
 
    We place DSL equipment both at the customer premises -- a residence or
business -- and in the central office that services that specific customer
premises. There are typically many incumbent carrier central offices in each
metropolitan area. We connect the DSL equipment in each central office to one of
our Metro Service Centers so that we can route or switch network traffic to
either a local destination, a national destination where we provide service or
the Internet.
 
    For our local connection services, the speed and effectiveness of the DSL
connection will vary based on a number of factors, including the distance of the
end user from the central office and the condition of the copper line that
connects the end user to the central office. However, the specific
 
                                       39
<PAGE>
number of potential users for higher speeds will vary by central office and by
region and will be affected by line quality. In the future, we intend to examine
adding a variety of high-speed local access technologies as they are developed,
including emerging wireless technologies. The chart below compares the
performance and range for our local connection services as of February 1999:
 
<TABLE>
<CAPTION>
 SPEED TO    SPEED FROM    RANGE(1)
 END USER     END USER      (FEET)     TECHNOLOGY(2)
- -----------  -----------  -----------  -------------
<C>          <S>          <C>          <C>
   144 Kbps  144 Kbps       Unlimited  IDSL(3)
   256 Kbps  256 Kbps          18,000  SDSL
   384 Kbps  384 Kbps          15,000  RADSL
   512 Kbps  512 Kbps          14,000  RADSL
   768 Kbps  768 Kbps          12,000  RADSL
     1 Mbps  1 Mbps            12,000  RADSL
   1.5 Mbps  1.5 Mbps           8,000  SDSL
     3 Mbps  1 Mbps            10,700  RADSL
     5 Mbps  1 Mbps             9,000  RADSL
   7.1 Mbps  1 Mbps             7,800  RADSL
</TABLE>
 
- ------------------------
 
(1) Estimated maximum distance from the central office to the end user.
 
(2) The technologies are described more fully in "--DSL Technologies" below.
 
(3) Speeds are 128 Kbps under certain circumstances.
 
    METROPOLITAN AREA AND WIDE AREA INTER-NETWORK CONNECTIONS
 
    For our business and service provider customers, we offer high-speed
connections both within and among metropolitan areas. In order to switch and
route traffic aggregated from each central office to its ultimate local or long
distance destination, we offer two interconnection services.
 
    Our 1.544 Mbps service -- DS-1 -- is suitable for small business customers
or service providers. Our 45 Mbps service -- DS-3 -- is intended for large
business customers or service providers. The monthly service charge for both
services is greater if traffic aggregated in one metropolitan area is terminated
in another metropolitan area, and varies based on the speed of the local access
connection.
 
    Our wide area network currently operates between each of the metropolitan
areas in which we provide service, and is currently a frame relay network which
we lease from a long distance carrier. In the future, we expect to add
Asynchronous Transfer Mode capability.
 
    NETWORK-ENABLED SERVICES, FEATURES AND APPLICATIONS
 
    We intend to use our high-speed local access connection to provide multiple
network services, features and applications. Instead of just providing a
high-speed access connection, we intend to offer many network-enabled features
and applications, which we are able to configure to meet each user's needs. We
believe our strategy to provide additional network services, features and
applications for each user on our network allows us to address a larger market
opportunity than the market opportunity represented by connection services
alone. Our strategy is to benefit from additional recurring monthly revenue by
providing multiple network features and applications.
 
    The features and applications that we currently offer are outlined below.
 
    - CORPORATE TELEPHONE SYSTEM EXTENSION.  This feature extends the
      functionality of the corporate telephone system directly into a
      teleworker's home or, in the future, a company's branch office. This
      feature supports common corporate telephone functions such as four digit
      dialing, conference calling and speed dialing. Benefits to our business
      customers include increased
 
                                       40
<PAGE>
      worker productivity, reduced second line expenses for voice service and
      the ability to aggregate and control long distance charges.
 
    - COMPUTER BACKUP.  The computer backup feature allows end users to
      automatically backup data to a secure remote site. Computer backup
      leverages our "always on," high-speed local access connection and allows
      the backup to be done at the times most convenient for the end user. We
      believe this feature is more cost effective than substitutes such as tape
      drives and disk cartridge drives, and has the additional protection of
      being stored off site. This application is provided by a third party,
      @Backup, Inc.
 
    - CONTENT CACHING.  We offer content caching for our customers' end users
      who access the Internet. This network feature operates in the background,
      serving user requests for Web pages locally rather than obtaining the
      content from the actual server across the Internet. Caching enables our
      customers to retrieve content faster than would otherwise be possible. Our
      caching solution requires no configuration setup by our customer. If the
      cache fails in any way, it will be automatically bypassed and user
      requests will be sent directly to the Internet.
 
    - SERVICE SELECTION.  We have implemented a service selection feature within
      our network that enables end users to access multiple destinations,
      including the corporate local area network, the corporate telephone
      system, the Internet, customers, suppliers and partners. Using this
      feature, a connection to the Internet and the corporate local area network
      can be established simultaneously by different users over the same DSL
      access line. This feature alleviates the corporate network from servicing
      Internet traffic to a teleworker.
 
    - DYNAMIC HOST CONFIGURATION PROTOCOL FUNCTIONALITY.  This feature relieves
      network administrators from the burden of notifying each teleworker of
      network configuration changes. Through the use of this protocol, once
      teleworkers start up their computers, the customer's server automatically
      downloads all of his or her network configuration parameters. If any
      modifications to the configuration are necessary, they only need to be
      modified once by the network administrator, and the network configuration
      parameters will be automatically distributed to all of the organization's
      teleworkers.
 
    - TURNKEY INTERNET.  This application allows small and medium businesses or
      large business branch offices the ability to host Internet and intranet
      Web sites. This application includes network equipment on the customer
      premises that provides router, Web server, e-mail, file server, firewall
      and Web-page caching. This premises-based Internet solution is combined
      with our "always on" high-speed network connection and Internet services
      from an Internet Service Provider customer.
 
    In the future, we plan to continue to expand our network features and
applications by working closely with leading hardware, software and networking
companies. We expect to focus on many applications, including combining voice
and data communications, increasing our directory and security capabilities, and
providing businesses with the ability to access their important applications
from remote locations. We have agreed to jointly develop directory and
voice-over Internet Protocol applications with Cisco. In addition, as part of
our strategic agreement with MCI WorldCom, we expect to jointly develop multiple
applications using DSL technology including voice and data applications over a
single DSL connection. Our strategic relationship with Microsoft will focus on
delivering co-branded network applications that will facilitate our customers'
access to the Internet and other destinations.
 
    Using these network-enabled features and applications, we can assemble a
broad solution to meet our business customer needs. For example, for a
teleworker, we might combine high-speed access to the corporate network and the
Internet with computer backup and corporate telephone extension. For a small
business, we might offer a turnkey Internet solution by combining high-speed
access to the Internet through our Internet Service Provider customer, with
customer premise equipment that supports Web server, e-mail, file server,
firewall, Web-page caching and network backup.
 
                                       41
<PAGE>
    TURNKEY SOLUTION
 
    We offer a full service solution for the configuration, provisioning, and
installation of the local access connection at the end user location, for which
the customer pays a one-time charge. That charge covers the cost of installing
the DSL line, any required inside wiring, the DSL modem, attaching the DSL modem
to either a single computer, local area network or enterprise server,
installation of a single network interface card if required, and installing the
TCP/IP software if required. For our large business customers, we provide
complete project management, including design, implementation and results
reporting. In some cases we seamlessly link our network operations systems to
existing customer information systems through Web-based interfaces.
 
CUSTOMERS, SALES AND MARKETING
 
    We offer our services to large, medium and small businesses. As of January
31, 1999, we served more than 75 business and 20 service provider customers. For
these business and service provider customers we have over 650 lines in service
and are under contract to supply over 9,000 additional DSL lines. Selected
business customers include Cisco, Silicon Graphics and QUALCOMM. In addition,
our service provider customers include CTSNet, ConnectNet, Verio, Epoch
Networks, Inc. and Ingram Micro.
 
    DIRECT SALES CHANNELS
 
    We market our services to large businesses through a direct sales force. Our
target account profile is a large, information-intensive enterprise with
multiple locations and large numbers of distributed workers. Our sales force
seeks to deal directly with the Chief Information Officer and the
telecommunications manager responsible for remote access in the target account.
Sales teams are deployed in each of the metropolitan areas in which we offer our
services. As of January 31, 1999, we had 40 sales and technical personnel
supporting our direct sales efforts. We intend to increase the size of our sales
and technical support force to sell and support large businesses as we enter new
geographic markets.
 
    Our relationship with large business customers can involve multiple phases.
A customer typically initially agrees to a first phase commitment for a specific
number of connections at a negotiated price and one year contract term.
Typically, three to six months into the first phase implementation, the customer
agrees to successive phases of implementation that could include additional
connections and upgrades in services, features and applications. In general, we
have experienced a six to nine month sales cycle prior to receiving significant
order volume from a business customer. We currently have two large business
customers that have committed to multi-phase implementation programs: Cisco and
Silicon Graphics. Collectively, these two customers account for over 90% of our
commitments to purchase our connections. Please see "Risk Factors--We cannot
predict our success because our business model is unproven."
 
                                       42
<PAGE>
    INDIRECT SALES CHANNELS
 
    We also market our services to small and medium businesses through indirect
channels, including Internet Service Providers, interexchange carriers,
competitive carriers, value-added resellers, and integrators. We offer each
service provider the ability to select those services that it would like to
bundle with its own service offerings to offer a total solution to its
customers. For example, Internet Service Providers typically combine our
high-speed connections with their Internet access services and resell the
combination to their existing and new customers. We address these markets
through sales and marketing personnel dedicated to each of these indirect
channels.
 
    We supplement our sales effort to certain of these service providers by
offering marketing support services that may include training, proposal
development, lead generation, channel support materials, joint marketing funds,
Web promotion, joint participation in national and regional customer events and
press announcements. We also offer promotions and sales incentives from time to
time to our service providers. Additionally, we support our service providers by
acting as a network integrator by qualifying potential customers for service,
ordering connections, installing equipment on the customer premises, turning up
the service, monitoring the network, troubleshooting, making repairs and
invoicing the customer on a single bill.
 
    Our agreements with our service provider customers vary widely. Generally,
our agreements have a one to three year term, and are based on negotiated prices
that decline with increasing levels of volume achievement. In many cases,
service providers have selected one or two, and perhaps three, DSL service
providers as preferred suppliers in each market. Our goal is to be selected as
the preferred supplier or one of the preferred suppliers in each metropolitan
area where we operate. When we are selected as a preferred supplier within a
given market, we may enter into joint marketing arrangements to promote our DSL
services. See "Risk Factors--We depend on third parties, particularly Microsoft,
MCI WorldCom and Cisco, for the marketing and sales of our network services."
 
CUSTOMER SERVICE
 
    We offer our business and service provider customers a single point of
contact for implementation, maintenance and billing. Our Network Operations
Center provides both proactive and customer initiated maintenance services 24
hours a day, seven days a week. We also provide a broad range of customer
service and Network Operations Center services through our Web interface.
 
    - IMPLEMENTATION. Working with a business or service provider customer, our
      customer service technicians and sales engineers will develop an
      implementation plan for each customer. The plan will include qualifying
      the customer for our service offerings, placing orders for the connection
      facilities, coordinating the delivery of the connection, installation and
      turn up.
 
    - MAINTENANCE. Our Network Operations Center in Denver provides network
      surveillance through standard Simple Network Management Protocol tools for
      all equipment in our network. Because we have complete end-to-end
      visibility of our network, we are able to proactively detect and correct
      the majority of our customer's maintenance problems remotely. Our goal is
      to proactively detect and repair 90% of our customer's maintenance
      problems before our customer is aware of a problem. Customer initiated
      maintenance and repair requests are managed and resolved primarily through
      the Customer Service Center. We utilize a trouble ticket management system
      to communicate customer maintenance problems from the customer service
      center to the Network Operations Center engineers and the field services
      engineers. Because our Network Operations Center is fully staffed 24 hours
      a day, seven days a week, we believe our ability to provide superior
      proactive maintenance is significantly enhanced.
 
                                       43
<PAGE>
    - BILLING. Customer bills are currently issued on a monthly basis through an
      internal billing system. Customer billing inquiries are managed by our
      Customer Service Center. In the future, billing inquiries will also be
      supported through our Web interface.
 
    - CUSTOMER SUPPORT SYSTEMS. Our system architecture is designed to
      facilitate rapid service responsiveness and reduce the cost of customer
      support. We use an integrated set of standard, off-the-shelf systems to
      support our business processes. We designed all business functions,
      including sales, ordering, provisioning, maintenance and repair, billing,
      accounting and decision support to use a single database, ensuring that
      every function has accurate, up-to-date information. The use of
      client-server tools and scalable Unix and Microsoft NT servers enables
      automation within and between processes.
 
NETWORK ARCHITECTURE
 
    NETWORK TECHNOLOGY
 
    The key design features allowing us to be a business-class network are:
 
    - CARRIER-CLASS NETWORK MANAGEMENT.  Our network is designed to be
      carrier-class throughout. For example, it has been designed with redundant
      network electronics and transmission paths. We have the ability to
      electronically view our entire network including the DSL modem located at
      the end user's computer or located on our customer's local area network
      from our Network Operations Center in Denver. We provide our business and
      service provider customers with service level agreements that guarantee
      specific levels of network performance. We have found that by offering
      service level agreements, we are better able to convince businesses to
      move their mission-critical applications onto our network.
 
    - SCALABLE SYSTEMS.  We use industry standard, off-the-shelf software to
      support preordering, ordering, provisioning, billing, network monitoring
      and trouble management. We have implemented these systems using a
      distributed client-server systems architecture that operates using a
      single, integrated database. This approach allows us to grow our customer
      support and network management capabilities as customer demand increases
      by giving our personnel faster, more accurate access to a fully integrated
      business information system.
 
    - NETWORK SECURITY.  Non-dedicated access, such as dial-up modem or
      integrated services digital network (ISDN) lines, or dedicated access to
      the public Internet, represents security risks for business networks.
      These security risks are mitigated through the use of virtual private
      network technologies such as authentication, tunneling, encryption, and
      through the use of permanent virtual circuits that define a logical
      dedicated connection between the end user and the corporate network. Our
      network enables businesses to fully employ these virtual private network
      technologies by using their own equipment at the edges of our network, or
      optionally purchasing virtual private networking services from us.
 
    NETWORK COMPONENTS
 
    Our network is an overlay network in that we lease existing transport
services from other service providers: local access copper lines from incumbent
carriers, metropolitan fiber from incumbent carriers or competitive carriers and
long-distance backbone fiber from long distance carriers. This overlay network
is designed to switch and route traffic within each metropolitan area, keeping
local traffic local and only sending non-local traffic over the wide area
network, thereby increasing overall network capacity and reliability and
reducing costs. The primary components of our network are customer
 
                                       44
<PAGE>
endpoint devices, local transport, our Connection Points, high-speed
metropolitan area network, our Metro Service Centers, our backbone and our
Network Operations Center.
 
    - CUSTOMER ENDPOINT DEVICES.  We currently offer DSL and private line local
      access connections in our network. For DSL access, we include the customer
      endpoint device -- the DSL modem -- as part of our complete turnkey
      service offering. We configure and install these modems with the end
      user's computer, or local area network or enterprise router along with any
      required on-site wiring needed to connect the modem to the telephone line
      leased from the incumbent carrier. Currently, almost all of the DSL modem
      and DSL multiplexing equipment we use for a single connection over a
      copper line must come from the same vendor since there are no existing
      interoperability standards for the equipment used in our higher speed
      services.
 
    - LOCAL TRANSPORT.  Our local transport connects customer end-point devices
      to our network. For digital subscriber line access, the transport is a
      DSL-capable copper loop leased by us from the incumbent carrier under
      terms specified in our interconnection agreements. In many cases, DSL-
      capable lines result from modification of voice grade lines to carry
      digital signals, at times involving an additional one-time or monthly
      charge relative to voice grade lines. For private line access, the
      transport is leased copper or fiber trunks provided by the incumbent
      carrier or a competitive carrier.
 
    - CONNECTION POINTS.  Through our interconnection agreements with the
      incumbent carriers, we secure collocation space in central offices. In
      each of these Connection Points, we connect the DSL-equipped copper loop
      to our DSL multiplexing equipment. Each of our Connection Points is
      designed to offer the same high reliability and availability standards as
      the incumbent carrier's own central office space. We expect to place our
      equipment in each of 30 to 90 central offices in any metropolitan area
      that we enter. As of January 31, 1999, we had Connection Points in nearly
      200 central offices. Although we expect that many Connection Points will
      be physically located within the central office, we have placed and will
      continue to place our Connection Points in locations immediately adjacent
      to central offices, when collocation space within the central office is
      not available.
 
    - HIGH-SPEED METROPOLITAN AREA NETWORK.  In each of our targeted
      metropolitan area markets, we operate a private metropolitan area network.
      The network consists of high-speed Asynchronous Transfer Mode
      communications circuits that we lease from competitive carriers or
      incumbent carriers to connect our Connection Points to the Metro Service
      Center. The metropolitan area network operates at 45 Mbps -- DS-3 --
      today, and can be upgraded to 150 Mbps -- OC-3 -- and 600 Mbps -- OC-12 --
      in the future. We anticipate leasing a substantial portion of this
      capacity from MCI WorldCom, as described in "--Strategic Partnerships."
 
    - METRO SERVICE CENTERS.  The Metro Service Center is a physical point of
      presence within a metropolitan area where local access traffic is
      aggregated from the Connection Points over our high-speed metropolitan
      area network. Although we generally expect to have one Metro Service
      Center in each of our targeted metropolitan areas, in larger metropolitan
      areas, we may have two. The Metro Service Center houses our Asynchronous
      Transfer Mode switches and Internet Protocol routers. We also place
      applications servers in our Metro Service Centers to support network
      enabled feature and applications. We design our Metro Service Centers for
      high availability including battery backup power, redundant equipment and
      active network monitoring.
 
    - BACKBONE.  Our backbone interconnects our Metro Service Centers so that
      communications traffic can be transported among different metropolitan
      areas. Currently, we lease a frame relay backbone from a long distance
      carrier. We anticipate leasing a substantial portion of this capacity from
      MCI WorldCom, as described in "--Strategic Partnerships." In the future,
      we expect to add Asynchronous Transfer Mode capability.
 
                                       45
<PAGE>
    - NETWORK OPERATIONS CENTER.  Our entire network is managed from the Network
      Operations Center located in Denver. From these centers, we provide
      end-to-end network monitoring and management using advanced network
      management tools 24 hours a day, seven days a week. This enhances our
      ability to address performance or connection issues before they affect our
      end user's experience. From the Network Operations Center, we monitor the
      equipment and circuits in each Metro Service Center, each metropolitan
      area network, each Connection Point, individual end user lines and modems.
      Please see "Risk Factors--A system failure or breach of network security
      could cause delays or interruptions of service to our customers."
 
    We are pursuing a program of ongoing network development. Our engineering
efforts focus on the design and development of new technologies and services to
increase the speed, efficiency, reliability and security of our network and to
enable network features and applications developed by us or by third parties.
Please see "Risk Factors--We may be unable to effectively expand our network
services and provide high performance to a substantial number of end users."
 
DSL TECHNOLOGIES
 
    We utilize various DSL equipment and technologies from different vendors.
The various DSL technologies allow us to offer a range of connection speeds.
Actual speeds are a function of the distance from the end user or local area
network to the central office and the quality of the copper line. We describe
the basic features and the market positioning of our primary DSL technologies
below.
 
    RATE ADAPTIVE DIGITAL SUBSCRIBER LINE (RADSL)
 
    RADSL technology allows each end user or local area network to utilize the
full digital capability of the underlying telephone line. Speeds reach up to 7.1
Mbps downstream and up to 1.1 Mbps upstream if the end user or local area
network is within 15,000 feet, or approximately 2.8 miles, from the central
office. We use this technology for end users or local area networks needing very
high access speeds. Our target customers for RADSL connections consist of small
and medium businesses and branch offices of large businesses needing T-1 or
higher speeds. We believe that these businesses often find the cost of dedicated
private line or frame relay services to be prohibitive. Our RADSL connection
competes favorably on a price/performance basis relative to traditional
fractional T-1 and frame relay services. The service also provides the highest
speed of any DSL service for bandwidth intensive applications.
 
    SYMMETRIC DIGITAL SUBSCRIBER LINE (SDSL)
 
    Our SDSL technology allows end users and local area network to achieve up to
1.5 Mbps speeds both downstream and upstream. Depending on the quality of the
copper line, 1.5 Mbps can typically be achieved if the end user or local area
network is within 8,000 feet, or approximately 1.5 miles, from the central
office.
 
    INTEGRATED DIGITAL SUBSCRIBER LINE (IDSL)
 
    IDSL technology allows us to reach all end users or local area networks
within a central office serving area irrespective of the end user or local area
network distance from the central office. Our IDSL service operates at up to 144
Kbps in each direction. This service can use existing integrated services
digital network (ISDN) equipment at the end user site, and is targeted at the
integrated services digital network (ISDN) replacement market. For information
intensive users, we believe that IDSL compares favorably with integrated
services digital network (ISDN) on a price/performance basis when the monthly
flat rate IDSL charge is compared with the per minute integrated services
digital network (ISDN) charge. We also offer IDSL to end users that have lines
that do not consist of continuous copper, such as digital line carrier equipped
lines that are partially copper and partially fiber.
 
                                       46
<PAGE>
COMPETITION
 
    We will face competition from many competitors with significantly greater
financial resources, well-established brand names and large, existing installed
customer bases. Moreover, we expect the level of competition to intensify in the
future. We expect significant competition from:
 
    - INCUMBENT CARRIERS. Incumbent carriers, such as GTE and U S WEST, are
      leasing wide area connections from long distance carriers, and have
      existing metropolitan area networks and circuit switched local access
      networks. Most incumbent carriers have announced deployment of commercial
      DSL services in certain areas. In addition, most incumbent carriers are
      combining their DSL service with their own Internet Service Provider
      businesses. We believe that incumbent carriers have the potential to
      quickly overcome many of the issues that have delayed widespread
      deployment of DSL services in the past. If a Regional Bell Operating
      Company is authorized to provide in-region long distance service in one or
      more states, by fulfilling the market-opening provisions of the 1996
      Telecommunications Act, the Regional Bell Operating Company may be able to
      offer "one stop shopping" that would be competitive with our offerings.
      The incumbent carriers have an established brand name in their service
      areas, possess sufficient capital to deploy DSL services rapidly and are
      in a position to offer service from central offices where we may be unable
      to secure collocation space.
 
    - TRADITIONAL INTEREXCHANGE CARRIERS. Many of the leading traditional
      interexchange carriers, such as AT&T, MCI WorldCom and Sprint, are
      expanding their capabilities to support high-speed, end-to-end networking
      services. Increasingly, their bundled services include high-speed local
      access combined with metropolitan and wide area networks, and a full range
      of Internet services and applications. We expect them to offer combined
      data, voice and video services over these networks.
 
     These carriers have deployed large scale networks, have large numbers of
     existing business and residential customers and enjoy strong brand
     recognition, and as a result represent significant competition. For
     instance, they have extensive fiber networks in many metropolitan areas
     that primarily provide high-speed data and voice communications to large
     companies. They could deploy DSL services in combination with their current
     fiber networks. They also have interconnection agreements with many of the
     incumbent carriers and have secured collocation spaces from which they
     could begin to offer competitive DSL services.
 
    - NEWER INTEREXCHANGE CARRIERS. The newer interexchange carriers, such as
      Williams, Qwest Communications International and Level 3 Communications,
      are building and managing high bandwidth, packet-based networks
      nationwide. They are also building direct sales forces and partnering with
      Internet Service Providers to offer services directly to business
      customers. They could extend their existing networks to include fiber
      metropolitan area networks and high-speed, off-net services using DSL,
      either alone, or in partnership with others.
 
    - CABLE MODEM SERVICE PROVIDERS. Cable modem service providers, like @Home
      Networks and its cable partners, are offering or preparing to offer
      high-speed Internet access over hybrid fiber coaxial cable networks to
      consumers. @Work has positioned itself to do the same for businesses.
      Where deployed, these networks provide local access services similar to
      our services, and in some cases at higher speeds. They typically offer
      these services at lower prices than our services, in part by sharing the
      bandwidth available on their cable networks among multiple end users.
 
    - WIRELESS AND SATELLITE DATA SERVICE PROVIDERS. Several new companies are
      emerging as wireless and satellite-based data service providers, over a
      variety of frequency allocations. These include:
 
       - WinStar Communications, Inc.,
 
       - Teligent, Inc.,
 
       - Teledesic LLC,
 
       - Hughes Space Communications, and
 
                                       47
<PAGE>
       - Iridium World Communications Ltd.
 
     These companies use a variety of new and emerging technologies, such as
     terrestrial wireless services, point-to-point and point-to-multipoint fixed
     wireless services, satellite-based networking and high-speed wireless
     digital communications.
 
    - INTERNET SERVICE PROVIDERS. Internet Service Providers provide Internet
      access to residential and business customers. These companies generally
      provide such Internet access over the incumbent carriers' circuit switched
      networks at integrated services digital network (ISDN) speeds or below.
      However, some Internet Service Providers, including HarvardNet, Inc. in
      Massachusetts, have begun offering DSL-based access using their own DSL
      services, or DSL services offered by the incumbent carrier or other
      DSL-based competitive carriers. Some Internet Service Providers have
      significant and even nationwide marketing presences and combine these with
      strategic or commercial alliances with DSL-based competitive carriers.
      Some Internet Service Providers, such as Concentric Network Corporation,
      Mindspring Enterprises, Inc., PSINet Inc. and Verio have significant and
      even nationwide presences.
 
    - COMPETITIVE CARRIERS. Certain competitive carriers, including Covad
      Communications Group, Inc. and NorthPoint Communications, Inc., have begun
      offering DSL-based data services. Other competitive carriers are likely to
      do so in the future. The 1996 Telecommunications Act specifically grants
      competitive carriers the right to negotiate interconnection agreements
      with incumbent carriers, including interconnection agreements which may be
      identical in all respects to our agreements.
 
    Many of these competitors are offering, or may soon offer, technologies and
services that will directly compete with some or all of our service offerings.
Such technologies include integrated services digital network (ISDN), DSL,
wireless data and cable modems. Please see "Risk Factors--The market in which we
operate is highly competitive, and we may not be able to compete effectively,
especially against established industry competitors with significantly greater
financial resources." Some of the competitive factors we face include:
 
       - transmission speed,
 
       - reliability of service,
 
       - breadth of service availability,
 
       - price performance,
 
       - network security,
 
       - ease of access and use,
 
       - content bundling,
 
       - customer support,
 
       - brand recognition,
 
       - operating experience,
 
       - ability to scale,
 
       - capital availability and
 
       - exclusive contracts.
 
INTERCONNECTION AGREEMENTS WITH INCUMBENT CARRIERS
 
    Interconnection agreements with incumbent carriers are critical to our
business. These agreements cover a number of aspects of our relationships with
incumbent carriers, including:
 
    - the price we pay to lease and the access we have to the incumbent
      carrier's copper lines;
 
    - the special conditioning the incumbent carrier provides on certain of
      these lines to enable the transmission of DSL signals;
 
    - the price and terms for collocation of our equipment in the incumbent
      carrier central offices;
 
    - the price we pay and the access we have to the incumbent carrier's
      transport facilities;
 
                                       48
<PAGE>
    - the ability we have to access conduits and other rights of way the
      incumbent carrier has to construct its own network facilities;
 
    - the operational support systems and interfaces that we can use to place
      orders and report and monitor the incumbent carrier's response to our
      requests;
 
    - the dispute resolution process we use with the incumbent carrier to
      resolve disagreements on the terms of the interconnection contract; and
 
    - the term of the interconnection agreement, its transferability to
      successors, its liability limits and other general aspects of our
      relationship with the incumbent carrier.
 
    We have signed interconnection agreements with six different major incumbent
carriers covering 23 states and the District of Columbia. In many cases,
incumbent carriers do not agree to the provisions in interconnection agreements
that we request, and we have not consistently prevailed in obtaining all of the
provisions we desire. We may be unable to continue to sign interconnection
agreements with incumbent carriers. If we are unable to enter into, or
experience delay in obtaining, interconnection agreements, this inability or
delay may materially and adversely affect our business and financial prospects.
The incumbent carriers are also permitting competitive carriers to adopt
previously signed interconnection agreements.
 
    Our interconnection agreements have a maximum term of three years, requiring
us to renegotiate the existing terms in the future. We may be unable to extend
our existing interconnection agreements or renegotiate new agreements on
favorable or any terms. In addition, our interconnection agreements are subject
to state commission, Federal Communications Commission and judicial oversight.
These bodies may modify the terms or prices of our interconnection agreements in
ways that would adversely affect our business and financial prospects.
 
GOVERNMENT REGULATION
 
    A significant portion of the services that we offer, particularly through
our wholly owned subsidiaries, ACI Corp. and ACI Corp.--Virginia, may be subject
to regulation at the federal, state and/or local levels. Future federal or state
regulations and legislation may be less favorable to us than current regulation
and legislation and therefore have a material and adverse impact on our business
and financial prospects. In addition, we may expend significant financial and
managerial resources to participate in proceedings setting rules at either the
federal or state level, without achieving a favorable result.
 
    FEDERAL LEGISLATION AND REGULATION
 
    The 1996 Telecommunications Act, enacted on February 8, 1996, substantially
departs from prior legislation in the telecommunications industry by
establishing local exchange competition as a national policy. This act removes
state regulatory barriers to competition and preempts laws restricting
competition in the local exchange market.
 
    The 1996 Telecommunications Act in some sections is self-executing, but in
addition, the Federal Communications Commission issues regulations that identify
specific requirements upon which we and our competitors rely in implementing the
changes it prescribes. The outcome of these various ongoing Federal
Communications Commission rulemaking proceedings or judicial appeals of such
proceedings could materially affect our business and financial prospects.
 
    The Federal Communications Commission prescribes rules applicable to
interstate communications, including rules implementing the 1996
Telecommunications Act, a responsibility it shares with the state regulatory
commissions. The 1996 Telecommunications Act, and the Federal Communications
Commission's initial rules interpreting such act, encouraged increased local
competition. A federal appeals court for the Eighth Circuit reviewed some of the
initial rules, and overruled some of its provisions, including some rules on
pricing and nondiscrimination. In January, 1999, the United States Supreme Court
reversed elements of the Eighth Circuit's ruling, finding that
 
                                       49
<PAGE>
the Federal Communications Commission has broad authority to interpret the 1996
Telecommunications Act and issue rules for its implementation, specifically
including authority over pricing methodology. The Supreme Court upheld the
Federal Communications Commission's orders to the incumbent carriers to combine
unbundled elements for competitors, and to allow competitors to pick and choose
among provisions in existing interconnection agreements. The Supreme Court also
found that the Federal Communications Commission's interpretation of the rules
for establishing unbundled elements was not consistent with the 1996
Telecommunications Act, and required the Federal Communications Commission to
reconsider its delineation of unbundled elements. The Federal Communications
Commission's replacement decision on unbundled elements may adversely affect our
business. In addition, some incumbent carriers may take the position that they
have no obligation to provide unbundled elements, including copper loops, until
the Federal Communications Commission issues new rules, which could adversely
affect our business.
 
    In November, 1998, the Federal Communications Commission ruled that DSL
services provided as dedicated access services in connection with interstate
services such as Internet access are interstate services subject to the Federal
Communications Commission's jurisdiction. This decision is currently subject to
reconsideration and appeal.
 
    In addition, in the spring of 1998, four of the Regional Bell Operating
Companies petitioned the Federal Communications Commission to be relieved of
certain regulatory requirements in connection with their own DSL services,
including obligations to unbundle DSL loops, but not the obligation to unbundle
the loops we purchase for our DSL services, and to resell DSL services. In
October 1998, the Federal Communications Commission ruled that DSL services are
telecommunications services subject to the requirements of the 1996
Telecommunications Act to unbundle such services and offer them for resale. In
October 1998, the Federal Communications Commission also issued a Notice of
Proposed Rulemaking indicating its intention to clarify expanded rights of
competitive carriers for collocation, access to copper loops, and various other
issues of consequence to competitive carriers deploying DSL services. The
Federal Communications Commission also indicated its intention to allow
incumbent carriers to create separate affiliates for their DSL businesses that
would have to operate as competitive carriers and would be permitted to operate
free of the resale and unbundling obligations of the 1996 Telecommunications
Act. These decisions are currently subject to reconsideration and appeal. The
final outcome of these decisions, originally scheduled to be announced on
January 28, 1999, has been postponed by the Federal Communications Commission
while it considers the impact of the Supreme Court's ruling on the 1996
Telecommunications Act. The final outcome of these petitions or other
proceedings interpreting the requirements of the 1996 Telecommunications Act may
adversely affect our business.
 
    STATE REGULATION
 
    Some of our services, particularly those of our subsidiaries, ACI Corp. and
ACI Corp.--Virginia, may be classified as intrastate services subject to state
regulation. All of the states where we operate, or will operate, require some
degree of state regulatory commission approval to provide certain intrastate
services. In most states, intrastate tariffs are also required for various
intrastate services, although we are not typically subject to price or rate of
return regulation for tariffed intrastate services. Actions by state public
utility commissions could cause us to incur substantial legal and administrative
expenses.
 
    Under the 1996 Telecommunications Act, if we so request, incumbent carriers
have a statutory duty to negotiate in good faith with us for agreements for
interconnection and access to unbundled network elements. These negotiations are
conducted on a region-wide basis, and individual agreements are then signed for
each of the states in the region for which we have made a request. We have
signed interconnection agreements with Ameritech, Bell Atlantic, BellSouth, GTE,
Pacific Bell and U S WEST. We have signed agreements with Ameritech for Illinois
and Michigan and currently are negotiating interconnection agreements for Ohio
and Wisconsin. We have signed agreements with Bell Atlantic for the District of
Columbia, Maryland, Massachusetts, New Jersey, New York, Pennsylvania and
Virginia.
 
                                       50
<PAGE>
We have signed agreements with BellSouth for Alabama, Arkansas, Florida,
Georgia, Kentucky, Louisiana, North Carolina, South Carolina and Tennessee. We
have signed an agreement with GTE for California and are currently completing
agreements for Florida, Minnesota, North Carolina, Oregon, Texas, Virginia and
Washington. We have signed an agreement with Pacific Bell for California. We
have signed agreements with U S WEST for Arizona, Colorado, Minnesota, Oregon,
and Washington and are currently negotiating an agreement for Utah. In addition,
we are currently negotiating with SBC Communications Inc. for Kansas and
Missouri and with Sprint for several states. These interconnection agreements
may not be on terms that are entirely satisfactory to us.
 
    During these negotiations, either the incumbent carrier or we may submit
disputes to the state regulatory commissions for mediation and, after the
expiration of the statutory negotiation period set forth in the 1996
Telecommunications Act, we may submit outstanding disputes to the states for
arbitration. We are currently arbitrating with SBC Communications Inc. in Texas
the terms of our interconnection agreement with Southwestern Bell for Texas. The
outcome of this arbitration may be unfavorable to us.
 
    Under the 1996 Telecommunications Act, states have begun and, in a number of
cases, completed regulatory proceedings to determine the pricing of unbundled
network elements and services, and the results of these proceedings will
determine the price we pay for, and whether it is economically attractive for us
to use, these elements and services.
 
    LOCAL GOVERNMENT REGULATION
 
    Should we in the future decide to operate our own transport facilities over
public rights-of-way, we may be required to obtain various permits and
authorizations from municipalities in which we operate such facilities. Some
municipalities may seek to impose similar requirements on users of transmission
facilities, even though they do not own such facilities. If municipal
governments impose conditions on granting permits or other authorizations or if
they fail to act in granting such permits or other authorizations, our business
could be adversely affected.
 
EMPLOYEES
 
    As of April 6, 1999, we had approximately 400 employees. We believe that our
future success will depend in part on our continued ability to attract, hire and
retain qualified personnel. Competition for such personnel is intense, and we
may be unable to identify, attract and retain such personnel in the future. None
of our employees are represented by a labor union or are the subject of a
collective bargaining agreement. We have never experienced a work stoppage and
believe that our employee relations are good.
 
PROPERTIES
 
    Our headquarters are located in facilities consisting of approximately
80,000 square feet in Englewood, Colorado, which we occupy under leases that
expire in October 1999 and January 2004. These leases may be extended. We also
lease space for network equipment installations in a number of other locations.
 
LEGAL PROCEEDINGS
 
    We are currently a party to an arbitration proceeding between us and SBC
Communications regarding the terms of interconnection with Southwestern Bell in
Texas. This arbitration, instituted December 11, 1998, is pending before the
Public Utility Commission of Texas. The dispute involves the terms and
conditions of issues related to DSL-based services and loops in connection with
our interconnection agreement with Southwestern Bell. We are seeking to compel
Southwestern Bell to include in our interconnection agreement language
comparable to that in our other interconnection
 
                                       51
<PAGE>
agreements, which gives us the ability to obtain copper telephone lines on which
we provide our chosen variety of DSL technologies.
 
    In addition, on March 12, 1999, our subsidiary ACI Corp. filed a complaint
with the Oregon Public Utilities Commission (the "Oregon PUC") against U S West
Communications regarding collocation matters. ACI has requested the Oregon PUC
to intervene in an on-going dispute between ACI and U S West Communications
regarding ACI's ability to collocate in three central offices located in
Portland, Oregon pursuant to Section 251(c)(6) of the 1996 Telecommunications
Act. ACI has requested that the Oregon PUC make a determination that U S West
Communications can, in fact, accommodate ACI's requests for collocation and, if
such a determination is made, that the Oregon PUC immediately order U S West
Communications to make space available to ACI on the terms and conditions set
forth in the existing interconnection agreement between the companies. ACI has
also sought monetary damages in an amount to be proven at a hearing to
compensate for ACI's economic losses. No hearing date or schedule has yet been
set for this proceeding.
 
    On February 18, 1999, we filed a complaint for declaratory relief in San
Diego County Superior Court (North County) against Thomas R. Lafleur. Mr.
Lafleur was a former employee who resigned and/or was terminated in 1998. After
he left, we sent him a check for the repurchase or buy-back of his unvested
shares; Mr. Lafleur refused to cash this check. The declaratory relief action is
to determine that his shares were unvested and thus properly repurchased. On or
about March 26, 1999, Mr. Lafleur filed an answer to the complaint and also
filed a cross-complaint against us for fraud, breach of the covenant of good
faith and fair dealing, conspiracy to inflict emotional distress, intentional
infliction of emotional distress, conversion and declaratory relief. The
cross-complaint seeks compensatory and punitive damages according to proof, and
438,115 shares of common stock. Mr. Lafleur alleges in his cross-complaint that
since we failed to purchase his shares within 60 days following his termination,
the terms of his stock purchase agreement prevent us from repurchasing his
shares. We intend to vigorously defend against such cross-claims, and intend to
file a demurrer to the cross-complaint. We are currently accounting for these
438,115 shares as treasury stock.
 
    In addition, we are subject to state commission, Federal Communications
Commission and court decisions as they relate to the interpretation and
implementation of the 1996 Telecommunications Act, the interpretation of
competitive carrier interconnection agreements in general and our
interconnection agreements in particular. In some cases, we may be deemed to be
bound by the results of ongoing proceedings of these bodies. We therefore may
participate in proceedings before these regulatory agencies or judicial bodies
that affect, and allow us to advance, our business plans.
 
                                       52
<PAGE>
                                   MANAGEMENT
 
DIRECTORS AND EXECUTIVE OFFICERS
 
    The following table sets forth, as of April 6, 1999, the names, ages and
positions of our executive officers and directors. Their respective backgrounds
are described below.
 
<TABLE>
<CAPTION>
                        NAME                               AGE                           POSITION(S)
- -----------------------------------------------------      ---      -----------------------------------------------------
<S>                                                    <C>          <C>
Catherine M. Hapka...................................          44   President, Chief Executive Officer and Director
 
Jeffrey Blumenfeld...................................          51   Vice President and General Counsel
 
Michael E. Calabrese.................................          33   Vice President, Sales Engineering
 
Scott C. Chandler....................................          37   Chief Financial Officer
 
Eric H. Geis.........................................          52   Vice President of National Deployment
 
James A. Greenberg...................................          38   Chief Network Officer
 
David J. Shimp.......................................          53   Chief Marketing Officer
 
Frank J. Tolve, Jr...................................          54   Chief Sales Officer
 
Kevin R. Compton.....................................          40   Director
 
Keith B. Geeslin.....................................          45   Director
 
Ken L. Harrison......................................          56   Director
 
Susan Mayer..........................................          48   Director
 
William R. Stensrud..................................          48   Director
 
John L. Walecka......................................          39   Director
 
Edward J. Zander.....................................          52   Director
</TABLE>
 
    All the officers identified above serve at the discretion of our Board of
Directors. There are no family relationships between any persons identified
above. The following are brief biographies of the persons identified above.
 
    CATHERINE M. HAPKA has been our President, Chief Executive Officer and a
director since June 1997. Prior to joining us, Ms. Hapka served as President of
NETS, Inc., an electronic commerce software company, from March 1997 to May
1997. Prior to joining NETS, Inc., Ms. Hapka served as Executive Vice President,
Markets, for U S WEST Communications, Inc. from January 1995 to October 1996. In
this capacity, Ms. Hapka led business and consumer telecommunications units
responsible for the voice, data, wireless, video and long distance businesses.
From 1991 to 1994, Ms. Hapka served as President and Chief Operating Officer of
the !NTERPRISE Networking Services Unit of U S WEST. Prior to joining U S WEST,
Ms. Hapka held general management positions with General Electric and McKinsey &
Co., Inc.
 
    JEFFREY BLUMENFELD has been our Vice President and General Counsel since
August 1997, and has been a partner in the Washington, D.C. law firm of
Blumenfeld & Cohen since 1984, which specializes in pro-competition advocacy for
technology-intensive companies. Since 1995, Mr. Blumenfeld has served as senior
trial counsel to the Antitrust Division of the U.S. Department of Justice in
several matters. Before starting Blumenfeld & Cohen in 1984, Mr. Blumenfeld held
positions with the U.S. Department of Justice from 1973 to 1984, most recently
as Chief of the U.S. V. AT&T staff of the Antitrust Division. Mr. Blumenfeld is
an adjunct professor of communications law at the Georgetown University Law
Center. Pursuant to his employment agreement, Mr. Blumenfeld has agreed to
expend approximately 24 hours a week in his capacity as one of our officers. For
more information on
 
                                       53
<PAGE>
Mr. Blumenfeld's relationship with us, please see "Certain Relationships and
Related Transactions-- Legal Services."
 
    MICHAEL E. CALABRESE has been our Vice President, Sales Engineering since
August 1998. Prior to joining us, Mr. Calabrese served in various positions at
Cisco Systems, Inc. from August 1995 to August 1998, most recently as Account
Manager of the Data Equipment Group. In that capacity, Mr. Calabrese maintained
primary responsibility for managing Cisco's major accounts. From January 1993 to
August 1995, Mr. Calabrese held management positions at Sprint Communications.
First, as Manager, Project Engineering, Mr. Calabrese led Sprint Communication's
new product rollouts. Subsequently, as Manager, Network Planner, Mr. Calabrese
was responsible for the design and build-out of Sprint Communications Data
Networks.
 
    SCOTT C. CHANDLER has served as our Chief Financial Officer since April
1998. From August 1996 to April 1998, Mr. Chandler served as President and Chief
Executive Officer of C-COR Electronics, Inc., a manufacturer of broadband
telecommunications equipment. From June 1990 to August 1996, Mr. Chandler served
in various positions at U S WEST and its subsidiaries, most recently as Vice
President and General Manager of U S WEST Cable and Multimedia from September
1995 to August 1996. While at U S WEST, Mr. Chandler also served as Vice
President and General Manager of the U S WEST subsidiary, !NTERPRISE AMERICA,
from January 1994 to August 1995 and as Director of Vendor Relations and Channel
Support of !NTERPRISE Networking Services from January 1992 to December 1993.
 
    ERIC H. GEIS has been our Vice President of National Deployment since
January 1, 1999. Prior to that, he served as our Vice President and General
Manager, Western Region beginning June 1997 and was a consultant to us from
April 1997 to June 1997. From November 1995 to December 1996, Mr. Geis served as
National Sales Director at GRC International, a producer and seller of wide area
data network design and optimization software applications. Between July 1990
and November 1995, Mr. Geis served as President and Chief Executive Officer of
Quintessential Solutions Inc., a provider of wide area network design, pricing
and optimization software applications for interexchange carriers, regional bell
operating companies, incumbent carriers, Internet Service Providers and major
corporate accounts. Mr. Geis was also Founder, President and Chief Executive
Officer of TeleQuest, Inc., a telecommunications products company from May 1983
to December 1990.
 
    JAMES A. GREENBERG has been our Chief Network Officer since July 1997. From
January 1990 to July 1997, Mr. Greenberg served in various positions at Sprint
Communications, most recently as Senior Director and interim Vice President of
the Data Operations and Engineering Group. In that capacity, Mr. Greenberg
directed the design, planning, operation and construction of Sprint's data
networks.
 
    DAVID J. SHIMP has served as our Chief Marketing Officer since October 1998.
Prior to joining us, Mr. Shimp was a partner at LAI Ward Howell, Inc., a
professional services firm, where he implemented that firm's first systems group
and was a leader in the technology department during his tenure from January
1991 to October 1998. Previously, Mr. Shimp held management positions at
McKinsey & Co. and the Deerpath Group.
 
    FRANK J. TOLVE, JR. has served as our Chief Sales Officer since December
1998. From November 1994 to September 1998, Mr. Tolve served as Vice President,
Sales Operations at Bay Networks. In that capacity, Mr. Tolve's responsibilities
included sales administration, channel strategy and worldwide
telesales/telemarketing. Mr. Tolve also served as Vice President, Sales
Operations for SynOptics Communications from November 1992 to November 1994.
 
    KEVIN R. COMPTON has been a director since July 1997. Since 1990, Mr.
Compton has served as a general partner of Kleiner Perkins Caufield & Byers, a
venture capital investment firm ("KPCB"). Mr. Compton is a director of Citrix
Systems, Inc., Digital Generation Systems, Inc., Global Village
 
                                       54
<PAGE>
Communication, Inc. and Corsair Communications, Inc., and is also a director of
several privately held companies. Mr. Compton was elected a director as the
nominee of KPCB, pursuant to the terms of a voting agreement.
 
    KEITH B. GEESLIN has been a director since July 1997. Since 1988, Mr.
Geeslin has served as a general partner of The Sprout Group, a venture capital
investment firm. Mr. Geeslin is a director of SDL, Inc., and is also a director
of several privately held companies, including Paradyne Corporation, a DSL
equipment manufacturer and supplier to us. Please see "Certain Relationships and
Related Transactions--Director Relationships." Mr. Geeslin was elected a
director as the nominee of The Sprout Group, pursuant to the terms of a voting
agreement.
 
    KEN L. HARRISON has been a director since March 1998. Since 1975, Mr.
Harrison has held various management positions at Portland General Electric
Company, where he currently serves as its Chairman and Chief Executive Officer,
a position he has held since December 1988. In addition, Mr. Harrison currently
serves as Vice Chairman and is a director of Enron Corp., a position he has held
since July 1997. Mr. Harrison has also served as Chairman of Enron
Communications Group, Inc. since September 1997, and as a director of Enron Oil
and Gas Corporation since October 1997. Mr. Harrison was elected a director as
the nominee of Enron, pursuant to the terms of a voting agreement.
 
    SUSAN MAYER has been a director since March 1999. Ms. Mayer is the President
of the MCI WorldCom Venture Fund and a Senior Vice President of MCI WorldCom
Inc. Previously, she was Senior Vice President of MCI Communications Corporation
from 1994 to 1998. From 1996 to 1997, Ms. Mayer was also President and Chief
Operating Officer of Sky MCI. From 1993 to 1994, Ms. Mayer was Vice President of
MCI Communications Corporation.
 
    WILLIAM R. STENSRUD has been a director since our inception in February 1997
and also served as our President and Chief Executive Officer from February 1997
to June 1997. Mr. Stensrud has been a general partner at the venture capital
investment firm of Enterprise Partners since January 1997. From June 1996
through December 1996, Mr. Stensrud served as President of Paradyne Corporation.
Previously, from February 1992 to March 1996, Mr. Stensrud served as President
and Chief Executive Officer of Primary Access Corporation. Mr. Stensrud is a
director of several privately held companies, including Paradyne Corporation.
Please see "Certain Relationships and Related Transactions--Director
Relationships." Mr. Stensrud was elected a director as the nominee of Enterprise
Partners, pursuant to the terms of a voting agreement.
 
    JOHN L. WALECKA has been a director since July 1997. Since 1984, Mr. Walecka
has been at Brentwood Venture Capital, a venture capital investment firm, and
has been a general partner since 1990. Mr. Walecka is a director of Documentum,
Inc. and Xylan Corporation, and is also a director of several privately held
companies. Please see "Certain Relationships and Related Transactions--Director
Relationships." Mr. Walecka was elected a director as the nominee of Brentwood
Venture Capital, pursuant to the terms of a voting agreement.
 
    EDWARD J. ZANDER has been a director since March 1999. Since 1987, Mr.
Zander has held various management positions at Sun Microsystems, Inc., where he
currently serves as its Chief Operating Officer, a position he has held since
February 1998. Mr. Zander is a director of Documentum, Inc. and one privately
held company.
 
    Members of the Board of Directors currently hold office and serve until our
next annual meeting of stockholders or until their respective successors have
been elected. The Board of Directors is currently comprised of eight directors
and, prior to the completion of this offering, will be classified into three
classes of directors serving staggered three-year terms, with one class of
directors to be elected at each annual meeting of stockholders. The
classification of directors has the effect of making
 
                                       55
<PAGE>
it more difficult to change the composition of the Board of Directors. See
"Description of Capital Stock--Possible Anti-Takeover Matters."
 
    All of our executive officers are appointed annually by and serve at the
discretion of the Board of Directors. All of our executive officers are at-will
employees.
 
COMMITTEES OF THE BOARD OF DIRECTORS
 
    We have a standing compensation committee currently composed of Messrs.
Walecka, Harrison and Stensrud. The compensation committee reviews and acts on
matters relating to compensation levels and benefit plans for our executive
officers and key employees, including salary and stock options. The compensation
committee is also responsible for granting stock awards, stock options and stock
appreciation rights and other awards to be made under our existing incentive
compensation plans. We also have a standing audit committee composed of Messrs.
Compton and Geeslin. The audit committee assists in selecting our independent
auditors and in designating services to be performed by, and maintaining
effective communication with, those auditors.
 
DIRECTOR COMPENSATION
 
    Directors do not receive compensation for services provided as a director or
for participation on any committee of the Board of Directors. All directors are
reimbursed for their out-of-pocket expenses in serving on the Board of Directors
or any committee thereof.
 
EXECUTIVE COMPENSATION
 
    The following table sets forth certain information with respect to the
compensation awarded to, earned by or paid to our current Chief Executive
Officer and our four other most highly compensated executive officers (the
"Named Executive Officers") during 1998 and 1997.
 
                           SUMMARY COMPENSATION TABLE
 
<TABLE>
<CAPTION>
                                                                                              LONG-TERM
                                                                                         COMPENSATION AWARDS
                                                                                      --------------------------
                                                            ANNUAL COMPENSATION         SECURITIES
                                                          -----------------------       UNDERLYING     ALL OTHER
NAME AND PRINCIPAL POSITION(S)                      YEAR   SALARY       BONUS           OPTIONS(#)     COMPENSATION
- --------------------------------------------------  ----  --------  -------------     --------------   ---------
<S>                                                 <C>   <C>       <C>               <C>              <C>
Catherine M. Hapka (1)............................  1998  $339,583  $     134,584         --             $--
  President, Chief Executive Officer and Director   1997   163,654         50,000       3,504,905(2)     --
                                                                                          365,094(3)
Michael E. Calabrese (4)..........................  1998    42,417        157,623(5)      360,000(2)        --
  Vice President, Sales Engineering                 1997     --          --               --             --
James A. Greenberg (6)............................  1998   145,000         31,538          48,000(2)     --
  Chief Network Officer                             1997    63,205         16,615         547,642(2)    50,000  (7)
Gloria A. Farler (8)..............................  1998   137,500         29,906          24,000(2)     --
  Vice President, Marketing Support                 1997    25,781          7,161          48,000(2)
Eric H. Geis (9)..................................  1998   136,000         29,580         --             --
  Vice President of National Deployment             1997    96,519         18,417         132,000(2)     --
</TABLE>
 
- ------------------------------
(1) Ms. Hapka has been employed by us since June 1997, and the amount listed
    sets forth her compensation since such date.
 
(2) Represents the number of shares of common stock that may be purchased upon
    the exercise of options.
 
(3) Represents a right to purchase 365,094 shares of Series A preferred stock,
    which she purchased in 1998.
 
(4) Mr. Calabrese has been employed by us since August 1998, and the amount
    listed sets forth his compensation since such date.
 
(5) Includes a cash payment of $150,000 to cover a signing bonus and relocation
    expenses.
 
(6) Mr. Greenberg has been employed by us since July 1997, and the amount listed
    sets forth his compensation since such date.
 
(7) Represents a flat fee relocation payment.
 
(8) Ms. Farler had been employed by us since October 1997; she resigned her
    position in February 1999.
 
(9) Mr. Geis has been employed by us since April 1997, and the amount listed
    sets forth his compensation since such date.
 
                                       56
<PAGE>
                             OPTION GRANTS IN 1998
 
    The following table sets forth information with respect to stock options
granted to each of the Named Executive Officers during 1998 pursuant to our 1997
Stock Option/Stock Issuance Plan. We did not grant any stock appreciation rights
to the Named Executive Officers during 1998.
 
<TABLE>
<CAPTION>
                                                                                                     POTENTIAL REALIZABLE
                                                          INDIVIDUAL GRANTS (1)                        VALUE AT ASSUMED
                                       ------------------------------------------------------------    ANNUAL RATES OF
                                        NUMBER OF     % OF TOTAL                                            STOCK
                                       SECURITIES       OPTIONS                                        APPRECIATION FOR
                                       UNDERLYING     GRANTED TO      EXERCISE                         OPTION TERM (3)
                                         OPTIONS       EMPLOYEES      PRICE PER                      --------------------
NAME                                     GRANTED      IN 1998 (2)       SHARE      EXPIRATION DATE      5%         10%
- -------------------------------------  -----------  ---------------  -----------  -----------------  ---------  ---------
<S>                                    <C>          <C>              <C>          <C>                <C>        <C>
Catherine M. Hapka...................      --             --             --              --             --         --
Michael E. Calabrese.................     360,000           10.7%     $    0.25   September 9, 2008  $  56,601  $ 143,437
James A. Greenberg...................      48,000            1.4%          0.25   September 9, 2008      7,547     19,125
Gloria A. Farler (4).................      24,000            0.7%          0.25   September 9, 2008      3,773      9,562
Eric H. Geis.........................      --             --             --              --             --         --
</TABLE>
 
- ------------------------------
(1) Options granted are immediately exercisable for all the option shares, but
    any shares purchased under such options will be subject to repurchase by us
    at such shares' option exercise price until they vest. Please see "--1997
    Stock Option/Stock Issuance Plan."
 
(2) We granted options to purchase 3,364,680 shares of common stock during 1998.
 
(3) Amount represents potential realizable value of option grants, assuming that
    our common stock appreciates at the annual rate shown, compounded annually,
    from the date of grant until expiration of the granted options. These
    numbers are calculated based on Securities and Exchange Commission
    requirements and do not reflect our projection or estimate of future stock
    price growth. Actual gains, if any, on stock option exercises are dependent
    on the future performance of our common stock.
 
(4) Ms. Farler resigned her position in February 1999.
 
                       FISCAL YEAR-END 1998 OPTION VALUES
 
    The following table provides information with respect to each of the Named
Executive Officers, concerning the exercise of common and preferred stock
options during 1998 and unexercised options held by them at the end of 1998.
 
<TABLE>
<CAPTION>
                                                                    NUMBER OF SECURITIES           VALUE OF UNEXERCISED
                                                                         UNDERLYING                      IN-THE-
                                                                   UNEXERCISED OPTIONS AT            MONEY OPTIONS AT
                                   SHARES                            DECEMBER 31, 1998             DECEMBER 31, 1998(1)
                                ACQUIRED ON        VALUE      --------------------------------  --------------------------
NAME                            EXERCISE(2)     REALIZED(3)   EXERCISABLE     UNEXERCISABLE     EXERCISABLE  UNEXERCISABLE
- -----------------------------  --------------  -------------  -----------  -------------------  -----------  -------------
<S>                            <C>             <C>            <C>          <C>                  <C>          <C>
Catherine M. Hapka...........     3,869,999(4)   $  73,019        --               --               --            --
Michael E. Calabrese.........        --             --           360,000           --            $1,440,000       --
James A. Greenberg...........       547,642(5)      --            48,000           --              192,000        --
Gloria A. Farler (6).........        43,200(7)      --            24,000           --               96,000        --
Eric H. Geis.................       132,000(8)      --            --               --               --            --
</TABLE>
 
- ------------------------------
 
(1) Amount based on the fair market value of our common stock on December 31,
    1998 as determined by our Board of Directors, less the exercise price
    payable for such shares.
 
(2) The shares of common stock were deposited in escrow with our corporate
    secretary where they continue to vest in accordance with the applicable
    vesting provisions. Please see "--1997 Stock Option/Stock Issuance Plan."
 
(3) Amount based on the fair market value, as determined by our Board of
    Directors, of our common stock and Series A preferred stock on the exercise
    date for such shares, less the exercise price paid for such shares.
 
(4) Ms. Hapka exercised all of these options in February 1998 for a net purchase
    price of $146,038 for common stock and $292,075 for Series A preferred
    stock. Ms. Hapka purchased the shares of Series A preferred stock at a $0.20
    per share discount from market value, for an aggregate discount of $73,019.
 
(5) Mr. Greenberg exercised all of these options in January 1998 for a net
    purchase price of $22,818.
 
(6) Ms. Farler resigned her position in February 1999.
 
(7) Ms. Farler exercised all of these options in March 1998 for a net purchase
    price of $1,800.
 
(8) Mr. Geis exercised all of these options in January 1998 for a net purchase
    price of $5,500.
 
                                       57
<PAGE>
EMPLOYMENT AGREEMENTS AND CHANGE IN CONTROL ARRANGEMENTS
 
    None of our employees are employed for a specified term, and each employee's
employment with us is subject to termination at any time by either party for any
reason, with or without cause.
 
    Ms. Hapka's employment agreement provides for a salary of $350,000 per year,
subject to periodic increases by the Board of Directors at its discretion. In
addition, it provides for a bonus potential of 50% of her base salary for her
second year of employment, which ends in June 1999, payable upon achievement of
certain milestones to be proposed by Ms. Hapka and agreed to by the Board of
Directors. In connection with her employment in June 1997, Ms. Hapka was granted
an option to purchase 3,504,905 shares of common stock at an exercise price of
$0.04 per share under the 1997 Stock Option/Stock Issuance Plan. Ms. Hapka
exercised such options in February 1998, subject to our right of repurchase
which lapses in accordance with the vesting schedule of the options. Please see
"--1997 Stock Option/Stock Issuance Plan." In connection with her employment,
Ms. Hapka was also given the right to purchase up to 365,094 shares of Series A
preferred stock at $0.80 per share. In February 1998, Ms. Hapka purchased these
shares for an aggregate purchase price of $292,075. We do not hold a right to
repurchase these shares of Series A preferred stock. In the event Ms. Hapka's
employment is terminated involuntarily and without cause, Ms. Hapka will be
entitled to receive a lump sum payment in an amount equal to her then-current
annual salary.
 
    Mr. Calabrese's employment agreement provides for an annual salary of
$130,000, subject to periodic increases by the Board of Directors at its
discretion. It provides for an annual bonus of up to 20% of his annual salary.
In addition, Mr. Calabrese received, as part of the acceptance of his
employment, a cash payment of $150,000, which also covered relocation expenses.
In the event Mr. Calabrese's employment is terminated involuntarily and without
cause during the first year of employment, which ends in August 1999, Mr.
Calabrese will be entitled to receive a payment equal to one year's base salary
payable in 12 monthly installments.
 
    Mr. Greenberg's employment agreement provides for an annual salary of
$145,000, subject to periodic increases by the Board of Directors at its
discretion.
 
    Mr. Geis' employment agreement provides for an annual salary of $136,000,
subject to periodic increases by the Board of Directors at its discretion. It
provides for an annual bonus of up to 25% of his base salary.
 
COMPENSATION COMMITTEE INTERLOCKS AND INSIDER PARTICIPATION
 
    Our Board of Directors currently has a compensation committee that reviews
and approves the compensation and benefits to be provided to our executive
officers and other key employees. In addition, the compensation committee
administers the 1997 Stock Option/Stock Issuance Plan. The compensation
committee currently consists of Messrs. Harrison, Stensrud and Walecka.
 
BENEFIT PLANS
 
1999 STOCK INCENTIVE PLAN
 
    Our 1999 Stock Incentive Plan is intended to serve as the successor equity
incentive program to the 1997 Stock Option/Stock Issuance Plan. The 1999 Stock
Incentive Plan was adopted by the board on March 16, 1999. Subject to
stockholder approval, the 1999 Stock Incentive Plan will become effective upon
effectiveness of the offering. All outstanding options under the 1997 Stock
Option/Stock Issuance Plan will at that time be incorporated into the 1999 Stock
Incentive Plan, and no further option grants will be made under the 1997 Stock
Option/Stock Issuance Plan. The incorporated options will continue to be
governed by their existing terms, unless the plan administrator elects to extend
one or more features of the 1999 Incentive Plan to those options. Except as
otherwise noted below, the incorporated options have substantially the same
terms as will be in effect for grants made under the Discretionary Option Grant
Program of the 1999 Stock Incentive Plan.
 
                                       58
<PAGE>
    An initial reserve of 8,161,944 shares of common stock has been authorized
for issuance under the 1999 Stock Incentive Plan. This share reserve consists of
(i) the number of shares estimated to remain available for issuance under the
1997 Stock Option/Stock Issuance Plan on the effective date of the new 1999
Stock Incentive Plan, including the shares subject to outstanding options
thereunder, plus (ii) an additional increase of approximately 5,500,000 shares.
The number of shares of common stock reserved for issuance under the 1999 Stock
Incentive Plan will automatically increase on the first trading day in January
each calendar year, beginning in calendar year 2000, by an amount equal to four
percent (4%) of the total number of shares of common stock outstanding on the
last trading day in December in the preceding calendar year, but in no event
will this annual increase exceed 2,880,000 shares. In addition, no participant
in the 1999 Stock Incentive Plan may be granted stock options, separately
exercisable stock appreciation rights and direct stock issuances for more than
900,000 shares of common stock in the aggregate per calendar year.
 
    The 1999 Stock Incentive Plan is divided into five separate components:
 
    - the Discretionary Option Grant Program, under which eligible individuals
      in our employ or service (including officers, non-employee board members
      and consultants) may, at the discretion of the plan administrator, be
      granted options to purchase shares of common stock at an exercise price
      not less than 100% of the fair market value of those shares on the grant
      date;
 
    - the Stock Issuance Program under which eligible individuals may, in the
      plan administrator's discretion, be issued shares of common stock
      directly, upon the attainment of designated performance milestones or upon
      the completion of a specified service requirement or as a bonus for past
      services;
 
    - the Salary Investment Option Grant Program, which may, at the plan
      administrator's sole discretion, be activated for one or more calendar
      years and, if so activated, will allow executive officers and other highly
      compensated employees the opportunity to apply a portion of their base
      salary each year to the acquisition of special below-market stock option
      grants;
 
    - the Automatic Option Grant Program, under which option grants will
      automatically be made at periodic intervals to eligible non-employee board
      members to purchase shares of common stock at an exercise price equal to
      100% of the fair market value of those shares on the grant date; and
 
    - the Director Fee Option Grant Program, which may, in the plan
      administrator's sole discretion, be activated for one or more calendar
      years and, if so activated, will allow non-employee board members the
      opportunity to apply a portion of the annual retainer fee otherwise
      payable to them in cash each year to the acquisition of special
      below-market option grants.
 
    The Discretionary Option Grant Program and the Stock Issuance Program will
be administered by the compensation committee. The compensation committee as
plan administrator will have complete discretion to determine which eligible
individuals are to receive option grants or stock issuances under those
programs, the time or times when the grants or issuances are to be made, the
number of shares subject to each grant or issuance, the status of any granted
option as either an incentive stock option or a non-statutory stock option under
the Federal tax laws, the vesting schedule to be in effect for the option grant
or stock issuance and the maximum term for which any granted option is to remain
outstanding. However, the board acting by disinterested majority will have the
exclusive authority to make any discretionary option grants or stock issuances
to members of the compensation committee. The compensation committee will also
have the exclusive authority to select the executive officers and other highly
compensated employees who may participate in the Salary Investment Option Grant
Program in the event that program is activated for one or more calendar years.
Neither the compensation committee nor the board will exercise any
administrative discretion with respect to option grants under the Salary
Investment Option Grant Program or under the Automatic Option Grant or Director
Fee Option Grant Program for the non-employee board members. All grants under
 
                                       59
<PAGE>
those latter three programs will be made in strict compliance with the express
provisions of each program.
 
    The exercise price for the shares of common stock subject to option grants
made under the 1999 Stock Incentive Plan may be paid in cash or in shares of
common stock valued at fair market value on the exercise date. The option may
also be exercised through a same-day sale program without any cash outlay by the
optionee.
 
    The plan administrator will have the authority to effect the cancellation of
outstanding options under the Discretionary Option Grant Program (including
options incorporated from the 1997 Stock Option/Stock Issuance Plan) in return
for the grant of new options for the same or different number of option shares
with an exercise price per share based upon the fair market value of the common
stock on the new grant date.
 
    Stock appreciation rights are authorized for issuance under the
Discretionary Option Grant Program. These rights will provide the holders with
the election to surrender their outstanding options for an appreciation
distribution from us equal to the excess of (i) the fair market value of the
vested shares of common stock subject to the surrendered option over (ii) the
aggregate exercise price payable for those shares. Such appreciation
distribution may be made in cash or in shares of common stock. None of the
incorporated options from the 1997 Stock Option/Stock Issuance Plan contain any
stock appreciation rights.
 
    In the event that we are acquired by merger or asset sale, each outstanding
option under the Discretionary Option Grant Program which is not to be assumed
by the successor corporation will automatically accelerate in full, and all
unvested shares under the Discretionary Option Grant and Stock Issuance Programs
will immediately vest, except to the extent our repurchase rights with respect
to those shares are to be assigned to the successor corporation. The plan
administrator will have complete discretion to grant one or more options under
the Discretionary Option Grant Program which will vest and become exercisable
for all the option shares in the event those options are assumed in the
acquisition and the optionee's service with us or the acquiring entity is
terminated within a designated period (not to exceed eighteen months) following
that acquisition. The vesting of outstanding shares under the Stock Issuance
Program may be accelerated upon similar terms and conditions.
 
    The plan administrator is also authorized to grant options and structure
repurchase rights so that the shares subject to those options or repurchase
rights will immediately vest in connection with a change in ownership or control
(whether by successful tender offer for more than fifty percent of our
outstanding voting stock or by a change in the majority of our board through one
or more contested elections for board membership). Such accelerated vesting may
occur either at the time of such change or upon the subsequent termination of
the individual's service within a designated period (not to exceed eighteen
months) following the change.
 
    The options to be incorporated from the 1997 Stock Option/Stock Issuance
Plan will immediately vest if we are acquired by merger or asset sale, unless
our repurchase rights with respect to the unvested shares subject to those
options are assigned to the successor entity. There are no other change in
control provisions currently in effect for those options. However, the plan
administrator will have the discretion to extend the acceleration provisions of
the 1999 Stock Incentive Plan to any or all of the options outstanding under the
1997 Stock Option/Stock Issuance Plan.
 
    In the event the plan administrator elects to activate the Salary Investment
Option Grant Program for one or more calendar years, each executive officer and
other highly compensated employee selected for participation may elect, prior to
the start of the calendar year, to reduce his or her base salary for that
calendar year by a specified dollar amount not less than $10,000 nor more than
$50,000. Each selected individual who files this timely election will
automatically be granted, on the first trading day in January of the calendar
year for which that salary reduction is to be in effect, a non-statutory option
to purchase that number of shares of common stock determined by dividing the
salary reduction amount by two-thirds of the fair market value per share of
common stock on the grant date. The
 
                                       60
<PAGE>
option will be exercisable at a price per share equal to one-third of the fair
market value of the option shares on the grant date. As a result, the total
spread on the option shares at the time of grant (the fair market value of the
option shares on the grant date less the aggregate exercise price payable for
those shares) will be equal to the amount of salary invested in that option. The
option will vest and become exercisable in a series of twelve equal monthly
installments over the calendar year for which the salary reduction is to be in
effect.
 
    Under the Automatic Option Grant Program, eligible non-employee board
members will receive a series of option grants over their period of board
service. Each individual who first becomes a non-employee board member at any
time at or after the effective date of this offering will receive an option
grant for 28,800 shares of common stock on the date such individual joins the
board, provided such individual has not been in our prior employ. In addition,
on the date of each annual stockholders meeting held after the effective date of
this offering, each non-employee board member who is to continue to serve as a
non-employee board member (including the individuals who are currently serving
as non-employee board members) will automatically be granted an option to
purchase 7,200 shares of common stock, provided such individual has served on
the board for at least six months. There will be no limit on the number of such
7,200 share option grants any one eligible non-employee Board member may receive
over his or her period of continued board service, and non-employee board
members who have previously been in our employ will be eligible to receive one
or more such annual option grants over their period of board service.
 
    Each automatic grant will have an exercise price per share equal to the fair
market value per share of common stock on the grant date and will have a term of
10 years, subject to earlier termination following the optionee's cessation of
board service. Each automatic option will be immediately exercisable for all of
the option shares; however, any unvested shares purchased under the option will
be subject to repurchase by the Company, at the exercise price paid per share,
should the optionee cease to serve on the board service prior to vesting in
those shares. The shares subject to each initial 28,800-share automatic option
grant will vest in a series of six successive equal semi-annual installments
upon the optionee's completion of each six-month period of board service over
the thirty-six-month period measured from the grant date. The shares subject to
each annual 7,200-share automatic grant will vest upon in two successive equal
semi-annual installments upon the optionee's completion of each six-month period
of board service measured from the grant date. However, the shares will
immediately vest in full upon certain changes in control or ownership or upon
the optionee's death or disability while a board member. Following the
optionee's cessation of board service for any reason, each option will remain
exercisable for a 12-month period and may be exercised during that time for any
or all shares in which the optionee is vested at the time of such cessation of
service.
 
    If the Director Fee Option Grant Program is activated in the future, each
non-employee board member will have the opportunity to apply all or a portion of
any annual retainer fee otherwise payable in cash to the acquisition of a
below-market option grant. The option grant will automatically be made on the
first trading day in January in the year for which the retainer fee would
otherwise be payable in cash. The option will have an exercise price per share
equal to one-third of the fair market value of the option shares on the grant
date, and the number of shares subject to the option will be determined by
dividing the amount of the retainer fee applied to the program by two-thirds of
the fair market value per share of common stock on the grant date. As a result,
the total spread on the option (the fair market value of the option shares on
the grant date less the aggregate exercise price payable for those shares) will
be equal to the portion of the retainer fee invested in that option. The option
will vest and become exercisable for the option shares in a series of twelve
equal monthly installments over the calendar year for which the election is to
be in effect. However, the option will become immediately exercisable and vested
for all the option shares upon (i) certain changes in the ownership or control
or (ii) the death or disability of the optionee while serving as a board member.
 
    The shares subject to each option under the Salary Investment Option Grant,
Automatic Option Grant and Director Fee Option Grant Programs will immediately
vest upon (i) an acquisition of us by
 
                                       61
<PAGE>
merger or asset sale or (ii) the successful completion of a tender offer for
more than 50% of our outstanding voting stock or a change in the majority of our
board effected through one or more contested elections for board membership.
 
    Limited stock appreciation rights will automatically be included as part of
each grant made under the Automatic Option Grant, Salary Investment Option Grant
and Director Fee Option Grant Programs and may be granted to one or more
officers as part of their option grants under the Discretionary Option Grant
Program. Options with this limited stock appreciation right may be surrendered
to us upon the successful completion of a hostile tender offer for more than 50%
of our outstanding voting stock. In return for the surrendered option, the
optionee will be entitled to a cash distribution from us in an amount per
surrendered option share equal to the excess of (i) the highest price per share
of common stock paid in connection with the tender offer over (ii) the exercise
price payable for such share.
 
    The board may amend or modify the 1999 Stock Incentive Plan at any time,
subject to any required stockholder approval. The 1999 Stock Incentive Plan will
terminate on the earliest of (i) February 28, 2009, (ii) the date on which all
shares available for issuance under the 1999 Stock Incentive Plan have been
issued as fully-vested shares or (iii) the termination of all outstanding
options in connection with certain changes in control or ownership of us.
 
1999 EMPLOYEE STOCK PURCHASE PLAN
 
    Our 1999 Employee Stock Purchase Plan was adopted by the board on March 16,
1999. Subject to stockholder approval, the 1999 Employee Stock Purchase Plan
will become effective immediately upon the execution of the Underwriting
Agreement for this offering. The plan is designed to allow our eligible
employees and those of our participating subsidiaries to purchase shares of
common stock, at semi-annual intervals, through their periodic payroll
deductions under the plan.
 
    One million two hundred thousand shares (1,200,000) of common stock will
initially be reserved for issuance under the plan. The reserve will
automatically increase on the first trading in January each year, beginning with
calendar year 2000, by an amount equal to one percent of the total number of
outstanding shares of our common stock on the last trading day in December in
the immediately preceding calendar year, but in no event will any such annual
increase exceed 780,000 shares.
 
    The plan will be implemented in a series of successive offering periods,
each with a maximum duration of 24 months. However, the initial offering period
will begin on the execution date of the Underwriting Agreement and will end on
the last business day in April 2001. The next offering period will commence on
the first business day in May 2001, and subsequent offering periods will
commence as designated by the plan administrator.
 
    Individuals who are eligible employees (scheduled to work more than 20 hours
per week for more than five calendar months per year) on the start date of any
offering period may enter the plan on that start date or on any subsequent
semi-annual entry date (the first business day of May or November each year).
Individuals who become eligible employees after the start date of the offering
period may join the plan on any subsequent semi-annual entry date within that
offering period.
 
    Payroll deductions may not exceed 15% of the participant's cash earnings,
and the accumulated payroll deductions of each participant will be applied to
the purchase of shares on his or her behalf on each semi-annual purchase date
(the last business day in April and October each year) at a purchase price per
share equal to 85% of the lower of (i) the fair market value of the common stock
on the participant's entry date into the offering period or (ii) the fair market
value on the semi-annual purchase date. In no event, however, may any
participant purchase more than 900 shares on any semi-annual purchase date, nor
may all participants in the aggregate purchase more than 300,000 shares on any
semi-annual purchase date.
 
                                       62
<PAGE>
    If the fair market value per share of our common stock on any purchase date
is less than the fair market value per share on the start date of the two-year
offering period, then that offering period will automatically terminate, and a
new two-year offering period will begin on the next business day, with all
participants in the terminated offering to be automatically transferred to the
new offering period.
 
    Should we be acquired by merger, sale of substantially all its assets or
sale of securities possessing more than fifty percent of the total combined
voting power of our outstanding securities, then all outstanding purchase rights
will automatically be exercised immediately prior to the effective date of an
acquisition. The purchase price will be equal to 85% of the lower of (i) the
fair market value per share of common stock on the participant's entry date into
the offering period in which an acquisition occurs or (ii) the fair market value
per share of common stock immediately prior to an acquisition. The limitation on
the maximum number of shares purchasable in the aggregate on any one purchase
date will not be in effect for any purchase date attributable to such an
acquisition.
 
    The plan will terminate on the earlier of (i) the last business day of April
2009, (ii) the date on which all shares available for issuance under the plan
shall have been sold pursuant to purchase rights exercised thereunder or (iii)
the date on which all purchase rights are exercised in connection with an
acquisition of us by merger or asset sale.
 
    The board may at any time alter, suspend or discontinue the plan. However,
certain amendments may require stockholder approval.
 
LIMITATION ON LIABILITY AND INDEMNIFICATION MATTERS
 
    Our certificate of incorporation limits the liability of directors to the
maximum extent permitted by Delaware law. In addition, our bylaws require us to
indemnify our directors and officers, and allow us to indemnify our other
employees and agents, to the fullest extent permitted by law. We have also
entered into agreements to indemnify our directors and certain executive
officers. We believe that these provisions and agreements are necessary to
attract and retain qualified directors and executive officers. At present, there
is no pending litigation or proceeding involving any director, officer, employee
or agent where indemnification will be required or permitted. We are not aware
of any threatened litigation or proceeding that might result in a claim for such
indemnification. Insofar as indemnification for liabilities arising under the
Securities Act may be permitted to directors, officers or persons controlling
our company pursuant to the foregoing provisions, we have been informed that, in
the opinion of the Securities and Exchange Commission, such indemnification is
against public policy as expressed in the Securities Act and is therefore
unenforceable.
 
                                       63
<PAGE>
                 CERTAIN RELATIONSHIPS AND RELATED TRANSACTIONS
 
SERIES A PURCHASE AGREEMENT
 
    On July 3, 1997, we entered into a Series A Preferred Stock Purchase
Agreement with Enterprise Partners, Brentwood Venture Capital, Kleiner Perkins
Caufield & Byers, The Sprout Group and certain other investors (together, the
"Series A Purchasers"). In a series of three closings, the Series A Purchasers
purchased in the aggregate 12,280,000 shares of our Series A preferred stock for
an aggregate purchase price of $12.3 million, which will convert into 29,472,000
shares of common stock upon the closing of this offering. Also, pursuant to a
Subsequent Closing Purchase Agreement dated as of December 23, 1997, we sold an
additional 210,000 shares of our Series A preferred stock to certain other
investors (the "Additional Series A Purchasers") for an aggregate purchase price
of $210,000, which will convert into 504,000 shares of common stock upon the
closing of this offering. In connection with these sales, we entered into an
Investors' Rights Agreement and Addendum with the Series A Purchasers and the
Additional Series A Purchasers, which provided the Series A Purchasers and
Additional Series A Purchasers with certain demand and piggyback registration
rights, and certain rights of first offer in the event we propose to offer for
sale certain of our securities. This investors' rights agreement and addendum
has been superseded by the 1999 Investors' Rights Agreement. Please see
"--Investors' Rights Agreement" and "Description of Capital Stock--Registration
Rights."
 
    In connection with an employment agreement between us and Catherine Hapka,
we issued 365,094 shares of Series A preferred stock at a purchase price of
$0.80 per share to Ms. Hapka, which will convert into 876,226 shares of common
stock upon the closing of this offering. Please see "Management--Employment
Agreements and Change in Control Arrangements."
 
SERIES B PURCHASE AGREEMENT
 
    On March 12, 1998, we entered into a Series B Preferred Stock Purchase
Agreement with certain of the Series A Purchasers and Enron Communications
Group, Inc. (together, the "Series B Purchasers"). Under this agreement, the
Series B Purchasers acquired an aggregate of 4,044,943 shares of Series B
preferred stock for an aggregate purchase price of $18.0 million, which will
convert into 9,707,863 shares of common stock upon the closing of this offering.
In connection with the Series B Preferred Stock Purchase Agreement, we entered
into an Amended and Restated Investors' Rights Agreement with the Series A
Purchasers, the Additional Series A Purchasers and the Series B Purchasers on
March 12, 1998. This agreement replaced the investors' rights agreement and
addendum from the Series A preferred stock financing and has been superseded by
the 1999 Investors' Rights Agreement. Please see "--Investors' Rights
Agreement."
 
SERIES C PURCHASE AGREEMENT; OTHER AGREEMENTS WITH MCI WORLDCOM
 
    In March 1999, we entered into a Series C Preferred Stock and Warrant
Purchase Agreement with MCI WorldCom's investment fund, pursuant to which the
fund acquired, for an aggregate purchase price of $30.0 million, 3,731,410
shares of Series C preferred stock, which are convertible into 4,477,692 shares
of common stock, and a warrant to purchase an aggregate of 720,000 shares of our
common stock at $6.70 per share. In April 1999, we issued to MCI WorldCom's
investment fund a warrant to purchase an additional 136,996 shares of common
stock at the purchase price per share paid in this offering. In connection with
this purchase agreement, we entered into an Amended and Restated Investors'
Rights Agreement, which has been superseded by the 1999 Investors' Rights
Agreement from the Qwest investment. Please see "--Investors' Rights Agreement."
 
    The MCI WorldCom investment was part of a broader strategic arrangement
between us and MCI WorldCom. As part of this strategic arrangement, we also
entered into an agreement with MCI WorldCom which designates us as MCI
WorldCom's preferred provider of business DSL lines in certain circumstances,
and which provides that MCI WorldCom is committed to sell at least 100,000 of
our
 
                                       64
<PAGE>
DSL lines over a period of five years, subject to penalties for failure to reach
target commitments. In turn, we have designated MCI WorldCom as our preferred
provider of network services. See "Business--Strategic Partnerships."
 
SERIES C PURCHASE AGREEMENT; OTHER AGREEMENTS WITH MICROSOFT
 
    In March 1999, we entered into a Series C Preferred Stock and Warrant
Purchase Agreement with Microsoft, pursuant to which Microsoft acquired, for an
aggregate purchase price of $30.0 million, 3,731,409 shares of Series C
preferred stock, which are convertible into 4,477,691 shares of common stock,
and a warrant to purchase an aggregate of 720,000 shares of our common stock at
a purchase price of $6.70 per share. In connection with this purchase agreement,
we entered into an Amended and Restated Investors' Rights Agreement dated March
16, 1999 which has been superseded by the 1999 Investors' Rights Agreement from
the Qwest investment. Please see "--Investors' Rights Agreement."
 
    The Microsoft investment was also part of a broader strategic arrangement.
As part of the Microsoft arrangement, we entered into an agreement in which
Microsoft agreed to jointly distribute with us a co-branded DSL version of the
Microsoft Network service focused on our small business customers. See
"Business--Strategic Partnerships."
 
SERIES C PURCHASE AGREEMENT AND SERIES D PURCHASE AGREEMENT; OTHER AGREEMENTS
WITH QWEST
 
    In connection with a broader customer relationship between us and Qwest, in
April 1999 we entered into a Series C Preferred Stock and Warrant Purchase
Agreement and a Series D Preferred Stock Purchase Agreement with U.S.
Telesource, Qwest's wholly-owned subsidiary. Pursuant to these agreements it
acquired, for an aggregate purchase price of approximately $15 million, 932,836
shares of Series C preferred stock, which are convertible into 1,119,403 shares
of common stock, 441,176 shares of Series D preferred stock, which are
convertible into 441,176 shares of common stock, and a warrant to purchase an
aggregate of 180,000 shares of our common stock at a purchase price of $6.70 per
share. In connection with these purchase agreements, we entered into an Amended
and Restated Investors' Rights Agreement (the "1999 Investors' Rights
Agreement"), that replaced the investors' rights agreement from the Microsoft
investment. Please see "--Investors Rights Agreement."
 
INVESTORS' RIGHTS AGREEMENT
 
    Pursuant to the terms of the 1999 Investors' Rights Agreement, the holders
of preferred stock acquired certain registration rights with respect to our
common stock. At any time after the earlier of (i) March 11, 2002 or (ii) six
months after the effective date of the first registration statement for a public
offering of our securities we file under the Securities Act:
 
    - holders of 60% or more of the registrable securities, as defined in the
      1999 Investors' Rights Agreement, may require us to register for public
      sale no less than 20% of their shares then outstanding; or
 
    - Enron may require us to register for public sale no less than 20% of our
      shares it then holds; or
 
    - MCI WorldCom's investment fund may require us to register for public sale
      no less than 20% of our shares it then holds.
 
    In addition, if certain competitors of MCI WorldCom or Qwest acquire greater
than 5% of our common stock, then MCI WorldCom's investment fund or Qwest's
wholly-owned subsidiary, as the case may be, may require us to register for
public sale all of its shares of our stock (each, a "Contingent
 
                                       65
<PAGE>
Demand for Registration"). Our Board of Directors may defer any of the above
demands for registration for a period up to 120 days. We are obligated to effect
only:
 
    - two such registrations pursuant to the request of holders of 60% or more
      of the registrable securities,
 
    - one such registration pursuant to the request of Enron,
 
    - one such registration pursuant to the request of MCI WorldCom's investment
      fund,
 
    - one Contingent Demand for Registration pursuant to the request of MCI
      WorldCom's investment fund, and
 
    - one Contingent Demand for Registration pursuant to the request of Qwest's
      subsidiary.
 
    In addition, if we propose to register securities under the Securities Act
after this offering, with certain exceptions, then any of the parties to the
Amended and Restated Investors' Rights Agreement has a right to request that we
register such holder's registrable securities, subject to quantity limitations
determined by underwriters if the offering involves an underwriting. All
registration expenses incurred in connection with the registrations described
above and all piggyback registrations will be borne by us. The participating
stockholders will pay for underwriting discounts and commissions incurred in
connection with any such registrations. We have agreed to indemnify the parties
to the agreement against certain liabilities in connection with any registration
effected pursuant to the 1999 Investors' Rights Agreement, including Securities
Act liabilities. Further, the holders of 40% or more of the registrable
securities may require us to register all or a portion of our registrable
securities on Form S-3 (a "Form S-3 Registration") when we qualify to file on
such form, provided that the aggregate proceeds of each such registration are at
least $5,000,000 and subject to certain other conditions and limitations,
including our ability to defer the filing of the Form S-3 Registration for a
period of not more than 120 days in certain circumstances. All expenses incurred
in connection with such a Form S-3 Registration shall be borne pro rata by the
stockholders participating in the Form S-3 Registration. All registration rights
will terminate no later than after five years following this offering. We have
agreed to indemnify the stockholders against certain liabilities in connection
with any registration effected pursuant to the 1999 Investors' Rights Agreement,
including liabilities under the Securities Act.
 
OFFERING OF NOTES AND WARRANTS
 
    On May 5, 1998, we closed a private placement of units consisting of $290
million aggregate principal amount at maturity of senior discount notes and
warrants to purchase 4,732,800 shares of our common stock. In October 1998, we
exchanged our senior discount notes for a like principal amount of 1998 Notes
that we registered under the Securities Act. Certain associates of Donaldson,
Lufkin & Jenrette Securities Corporation ("DLJSC"), an initial purchaser in the
May 1998 offering, own an aggregate of 3,000,000 shares of Series A preferred
stock and 449,438 shares of Series B preferred stock, which represent in the
aggregate approximately 13.5% of our outstanding equity.
 
    Of these, Sprout Capital VII, L.P. beneficially owns 2,609,686 shares of
Series A preferred stock and 390,966 shares of Series B preferred stock, which
represent in the aggregate approximately 11.7% of our outstanding equity. All of
the shares owned by Sprout Capital VII, L.P. are subject to a voting trust and
are held by an independent third party as trustee. The trustee will vote such
shares in its sole and absolute discretion as advised by an independent adviser
who is not affiliated with Sprout Capital VII, L.P. and DLJSC and subject to the
Amended and Restated Voting Agreement dated March 12, 1998.
 
    Also, pursuant to the Amended and Restated Voting Agreement, Sprout Capital
VII, L.P., The Sprout CEO Fund, L.P., DLJ Capital Corporation and DLJ First ESC
L.L.C., all of which are affiliates of DLJSC, collectively have the right to
designate one member of the Board of Directors. Their current
 
                                       66
<PAGE>
designee is Keith B. Geeslin. Mr. Geeslin is a Divisional Senior Vice President
of DLJ Capital Corporation, a wholly owned subsidiary of Donaldson, Lufkin &
Jenrette, Inc., the parent of DLJSC. Mr. Geeslin is also one of several
individuals who serve as general partners of DLJ Associates VII, L.P., which is
a general partner of Sprout Capital VII, L.P. DLJ Capital Corporation is the
managing general partner of each of Sprout Capital VII, L.P. and The Sprout CEO
Fund, L.P.
 
DIRECTOR RELATIONSHIPS
 
    William R. Stensrud, a member of our Board of Directors, also served as our
President and Chief Executive Officer from February 1997 through June 1997. Mr.
Stensrud and Mr. Geeslin, also a member of our Board of Directors, each also
serve as directors for Paradyne Corporation, one of our vendors. Additionally,
from June 1996 through December 1996, Mr. Stensrud served as President of
Paradyne Corporation. John L. Walecka, a member of our Board of Directors, also
serves as a director for Xylan Corporation, an indirect vendor to us. For the
period ended December 31, 1997 and for the year ended December 31, 1998, we made
purchases totaling approximately $419,000 and $13.0 million, respectively, from
Paradyne Corporation. We do not purchase any products directly from Xylan
Corporation; rather, our purchase of Xylan Corporation products is sourced
through Paradyne Corporation. We believe that our transactions with Paradyne
Corporation and Xylan Corporation were completed at rates similar to those
available from alternative vendors.
 
    Susan Mayer, a member of our Board of Directors, also serves as President of
MCI WorldCom's investment fund and a Senior Vice President of MCI WorldCom, Inc.
In March 1999, we entered into a strategic arrangement with MCI WorldCom, Inc.
As part of this strategic arrangement, MCI WorldCom's investment fund invested
$30.0 million in us. Please see "Business--Strategic Partnerships."
 
LEGAL SERVICES
 
    Jeffrey Blumenfeld, our Vice President and General Counsel, also serves as a
partner of Blumenfeld & Cohen, a law firm which performs legal services for us.
In connection with Mr. Blumenfeld's employment with us, we issued to him options
to purchase 438,115 shares of common stock at an exercise price of $0.04 per
share, which were exercised in January 1998. In addition, Mr. Blumenfeld and
certain other partners of Blumenfeld & Cohen purchased an aggregate of 140,000
shares of Series A preferred stock at $1.00 per share. For the period ended
December 31, 1997 and for the year ended December 31, 1998, we incurred expenses
for legal fees to Blumenfeld & Cohen of approximately $92,000 and $1.3 million,
respectively.
 
    Pursuant to the terms of a written employment agreement with Mr. Blumenfeld,
we have agreed to employ him as Vice President and General Counsel at an annual
salary of $110,000 for a minimum time commitment by Mr. Blumenfeld of 24 hours a
week. Under the terms of such agreement, Blumenfeld & Cohen has agreed to charge
us at a discount from its regular rates for legal services, including Mr.
Blumenfeld's time in excess of his minimum time commitment.
 
                                       67
<PAGE>
                             PRINCIPAL STOCKHOLDERS
 
    The following table sets forth certain information as of April 6, 1999 with
respect to the beneficial ownership of our common stock and as adjusted to
reflect the sale of shares of common stock in this offering by:
 
    - each person known by us to own beneficially more than five percent, in the
      aggregate, of the outstanding shares of our common stock, assuming the
      conversion of all preferred stock into common stock,
 
    - our directors and our Named Executive Officers, and
 
    - all executive officers and directors as a group.
 
Share ownership in each case includes shares issuable upon exercise of
outstanding options and warrants that are exercisable within 60 days of April 6,
1999 as described in the footnotes below. Percentage of ownership is calculated
pursuant to SEC Rule 13d-3(d)(1). Certain of the outstanding shares of our
capital stock are subject to a voting agreement. Unless otherwise indicated, the
address for each stockholder is c/o Rhythms NetConnections Inc., 6933 South
Revere Parkway, Englewood, Colorado 80112.
 
<TABLE>
<CAPTION>
                                                                                               PERCENTAGE BENEFICIALLY
                                                                                                        OWNED
                                                                                NUMBER OF      ------------------------
                                                                               BENEFICIALLY      BEFORE        AFTER
BENEFICIAL OWNER (1)                                                         OWNED SHARES (1)   OFFERING     OFFERING
- ---------------------------------------------------------------------------  ----------------  -----------  -----------
<S>                                                                          <C>               <C>          <C>
Brentwood Venture Capital (2)..............................................      8,278,651           13.5%        11.7%
Enterprise Partners (3)....................................................     10,440,415           17.1%        14.8%
Kleiner Perkins Caufield & Byers (4).......................................      8,278,651           13.5%        11.7%
MCI WorldCom Venture Fund, Inc. (5)........................................      5,334,688            8.6%         7.5%
The Sprout Group (6).......................................................      8,278,651           13.5%        11.7%
Enron Communications Group (7).............................................      5,393,258            8.8%         7.6%
Microsoft Corporation (8)..................................................      5,197,691            8.4%         7.3%
Catherine M. Hapka (9).....................................................      4,621,130            7.6%         6.5%
Michael E. Calabrese.......................................................        360,000          *            *
Eric H. Geis...............................................................        150,000          *            *
James A. Greenberg (10)....................................................        715,642            1.2%         1.0%
Gloria Farler (11).........................................................         30,000          *            *
Kevin R. Compton (12)......................................................         --             --           --
Keith B. Geeslin (13)......................................................         --             --           --
Ken Harrison (14)..........................................................         --             --           --
Susan Mayer (15)...........................................................         --             --           --
William R. Stensrud (16)...................................................         --             --           --
John L. Walecka (17).......................................................         --             --           --
Edward J. Zander...........................................................         --             --           --
All directors and executive officers as a group (16 persons) (18)..........      7,582,886           12.4%        10.7%
</TABLE>
 
- ------------------------------
 
   * Represents beneficial ownership of less than one percent of the outstanding
     shares of our common stock.
 
 (1) Except as indicated by footnote, we understand that the persons named in
     the table above have sole voting and investment power with respect to all
     shares shown as beneficially owned by them, subject to community property
     laws where applicable.
 
 (2) Consists of shares beneficially owned by Brentwood Affiliates Fund, L.P.
     and Brentwood Associates VII, L.P. (collectively, the "Brentwood
     Entities"). The address for the Brentwood Entities is 3000 Sand Hill Road,
     Building 1, Suite 260, Menlo Park, California 94025.
 
 (3) Consists of shares beneficially owned by Enterprise Partners III
     Associates, L.P., Enterprise Partners III, L.P. and Enterprise Partners IV,
     L.P. (collectively, the "Enterprise Entities"). The address for each of the
     Enterprise Entities is 7979 Ivanhoe, Suite 550, La Jolla, California 92037.
 
 (4) Consists of shares beneficially owned by Kleiner Perkins Caufield & Byers
     VIII, KPCB VIII Founders Fund and KPCB VIII Information Sciences Zaibatsu
     Fund II (collectively, the "KPCB Entities"). The address for each of the
     KPCB Entities is 2750 Sand Hill Road, Menlo Park, California 94025.
 
 (5) Includes 856,996 shares issuable upon exercise of warrants exercisable
     within 60 days of April 6, 1999. The address for MCI WorldCom Venture Fund,
     Inc. is 1801 Pennsylvania Avenue, Washington, D.C. 20006.
 
                                       68
<PAGE>
 (6) Consists of shares beneficially owned by DLJ Capital Corporation, DLJ First
     ESC L.L.C., Sprout Capital VII, L.P. and The Sprout CEO Fund, L.P.
     (collectively, the "Sprout Entities"). The address for each of the Sprout
     Entities is 3000 Sand Hill Road, Building 3, Suite 170, Menlo Park,
     California 94025. Of these, Sprout Capital VII, L.P. beneficially owns
     7,201,565 shares. All of the shares beneficially owned by Sprout Capital
     VII, L.P. are subject to a voting trust agreement and are held and voted by
     an independent third party, First Union Trust Company, National
     Association, as voting trustee. Please see "Certain Relationships and
     Related Transactions--Offering of Senior Discount Offering Notes and
     Warrants."
 
 (7) These shares are subject to a voting trust agreement. See "Description of
     Capital Stock--Board Representation Rights and Voting." The address for
     Enron Communications Group, Inc. is 210 Southwest Morrison Street, Suite
     400, Portland, Oregon 97204.
 
 (8) Includes 720,000 shares issuable upon exercise of a warrant exercisable
     within 60 days of April 6, 1999. The address for Microsoft Corporation is
     One Microsoft Way, Redmond, Washington 98052.
 
 (9) Includes shares held by Ms. Hapka's children, Christopher H. Safaya and
     Catherine A. Safaya, in the amount of 5,333 shares each and shares held by
     Christopher H. Safaya 1999 Trust and Catherine A. Safaya 1999 Trust in the
     amount of 120,000 shares each.
 
 (10) Includes 120,000 shares issuable upon exercise of options exercisable
      within 60 days of April 6, 1999.
 
 (11) Ms. Farler resigned in February 1999.
 
 (12) Excludes shares held by the KPCB Entities. Mr. Compton, as a General
      Partner of KPCB, may be deemed to have voting and investment power over
      the shares held by the KPCB Entities. Mr. Compton disclaims beneficial
      interest in such shares, except to the extent of his interest in the KPCB
      Entities.
 
 (13) Excludes shares held by the Sprout Entities. Mr. Geeslin, as a General
      Partner of The Sprout Group, may be deemed to have voting and investment
      power over the shares held by the Sprout Entities. Mr. Geeslin disclaims
      beneficial interest in such shares, except to the extent of his interest
      in the Sprout Entities.
 
 (14) Excludes shares held by Enron. Mr. Harrison, as Chairman of Enron, may be
      deemed to have voting and investment power over the shares held by Enron.
      Mr. Harrison disclaims beneficial interest in such shares, except to the
      extent of his interest in Enron.
 
 (15) Excludes shares held by MCI WorldCom's investment fund. Ms. Mayer, as
      President of MCI WorldCom's investment fund, may be deemed to have voting
      and investment power over the shares held by MCI WorldCom's investment
      fund. Ms. Mayer disclaims beneficial interest on such shares, except to
      the extent of her interest in MCI WorldCom's investment fund.
 
 (16) Excludes shares held by the Enterprise Entities. Mr. Stensrud, as a
      General Partner of Enterprise Partners, may be deemed to have voting and
      investment power over the shares held by the Enterprise Entities. Mr.
      Stensrud disclaims beneficial interest in such shares, except to the
      extent of his interest in the Enterprise Entities.
 
 (17) Excludes shares held by the Brentwood Entities. Mr. Walecka, as a General
      Partner of Brentwood Venture Capital, may be deemed to have voting and
      investment power over the shares held by the Brentwood Entities. Mr.
      Walecka disclaims beneficial interest in such shares, except to the extent
      of his interest in the Brentwood Entities.
 
 (18) Includes 120,000 shares issuable upon exercise of options or warrants
      exercisable within 60 days of April 6, 1999 and excludes shares held by
      the Brentwood Entities, the Enterprise Entities, the KPCB Entities, MCI
      WorldCom, the Sprout Entities, Enron Communications Group and Microsoft.
 
                                       69
<PAGE>
                          DESCRIPTION OF CAPITAL STOCK
 
    After this offering, we will be authorized to issue 250,000,000 shares of
common stock, $0.001 par value per share, of which 70,564,582 shares will be
issued and outstanding, 1,000,000 shares of Series 1 preferred stock, $0.001 par
value per share, of which no shares will be issued and outstanding and 4,000,000
shares of undesignated preferred stock, $0.001 par value per share, of which no
shares will be issued and outstanding.
 
COMMON STOCK
 
    As of April 6, 1999, there were 10,570,126 shares of common stock
outstanding and held of record by approximately 75 stockholders. The holders of
common stock are entitled to one vote for each share held of record on all
matters submitted to a vote of the stockholders. Subject to preferences that may
be applicable to any outstanding shares of preferred stock, holders of common
stock are entitled to receive ratably such dividends as may be declared by the
Board of Directors out of funds legally available. See "Dividend Policy." All
outstanding shares of common stock are fully paid and nonassessable.
 
PREFERRED STOCK
 
    After this offering of common stock, we may issue up to 1,000,000 shares of
Series 1 preferred stock and the Board of Directors will have the authority,
without further action by the stockholders, to issue 4,000,000 additional shares
of preferred stock in one or more series and to fix the rights, priorities,
preferences, qualifications, limitations and restrictions, including dividend
rights, conversion rights, voting rights, terms of redemption, terms of sinking
funds, liquidation preferences and the number of shares constituting any series
or the designation of such series, which could decrease the amount of earnings
and assets available for distribution to holders of common stock or adversely
affect the rights and powers, including voting rights, of the holders of the
common stock. The issuance of preferred stock could have the effect of delaying
or preventing a change in control or make removal of our management more
difficult. Additionally, the issuance of preferred stock may have the effect of
decreasing the market price of the common stock and may adversely affect the
voting and other rights of the holders of common stock. After this offering,
there will be no shares of preferred stock outstanding.
 
WARRANTS
 
    In connection with the issuance of the senior discount notes in May 1998, we
issued warrants to purchase an aggregate of 4,732,800 shares of common stock
with an exercise price of $0.004 per share. These warrants become exercisable on
May 4, 1999 and automatically expire on May 15, 2008. Following the occurrence
of a "repurchase event" as defined in the warrant agreement governing these
warrants, we must make an offer to repurchase for cash all outstanding warrants
issued in connection with the senior discount notes.
 
    In May 1998, we issued to Sun Financial Group Inc., now GATX Capital
Corporation, a warrant to purchase 574,380 shares of common stock with an
exercise price of $1.85 per share. In March 1999, we issued to GATX warrants to
purchase an additional 45,498 shares of common stock with an exercise price of
$10.55 per share. These warrants are immediately exercisable and expire on the
later of 10 years from the date of grant or five years after the closing of this
offering.
 
    In connection with its $30 million equity investment in us in March 1999, we
issued to MCI WorldCom's investment fund a warrant to purchase up to 720,000
shares of common stock at an exercise price of $6.70 per share. This warrant is
immediately exercisable and expires on March 2, 2004. In April 1999, we issued
to MCI WorldCom's investment fund a warrant to purchase an additional
 
                                       70
<PAGE>
136,996 shares of common stock at the per share exercise price equal to the
price per share paid in this offering. This warrant is immediately exercisable
and expires on April 4, 2004.
 
    In connection with its $30 million equity investment in us in March 1999, we
issued to Microsoft a warrant to purchase up to 720,000 shares of common stock
at an exercise price of $6.70 per share. This warrant is immediately exercisable
and expires on March 15, 2004.
 
    In connection with its $15 million equity investment in us in April 1999, we
issued to Qwest's wholly-owned subsidiary a warrant to purchase up to 180,000
shares of our common stock at an exercise price of $6.70 per share. This warrant
is immediately exercisable and expires on April 4, 2004.
 
    In April 1999, we issued to Cisco Systems Capital Corporation a warrant to
purchase up to 75,000 shares of common stock at an exercise price of $10.55 per
share. This warrant is immediately exercisable and expires on April 5, 2002.
 
REGISTRATION RIGHTS
 
    Pursuant to the terms of the 1999 Investors' Rights Agreement, the holders
of preferred stock acquired certain registration rights with respect to our
common stock. For a description of these rights, see "Certain Relationships and
Related Transactions--Investors' Rights Agreement."
 
    The holders of the warrants issued in connection with the senior discount
notes, GATX and Cisco are entitled to piggyback registration rights similar to
those described above. Furthermore, we are obligated to register, within 180
days following the consummation of this offering, the shares issuable upon
exercise of the warrants issued in connection with the senior discount notes and
to keep such registration statement effective for up to 120 days.
 
POSSIBLE ANTI-TAKEOVER MATTERS
 
    CERTIFICATE OF INCORPORATION AND BYLAWS
 
    Our certificate of incorporation authorizes our Board of Directors to
establish one or more series of undesignated preferred stock, the terms of which
can be determined by the Board of Directors at the time of issuance. See
"--Preferred Stock." Our certificate of incorporation also provides that all
stockholder action must be effected at a duly called meeting of stockholders and
not by a consent in writing. Our bylaws provide that our Board of Directors will
be classified into three classes of directors. Please see "Management--Directors
and Executive Officers." In addition, our bylaws do not permit our stockholders
to call a special meeting of stockholders; only our Chief Executive Officer,
President, Chairman of the Board or a majority of the Board of Directors are
permitted to call a special meeting of stockholders. Our bylaws also require
that stockholders give advance notice to our secretary of any nominations for
director or other business to be brought by stockholders at any stockholders'
meeting and require a supermajority vote of members of our Board of Directors
and/or stockholders to amend certain bylaw provisions. These provisions of the
certificate of incorporation and the bylaws could discourage potential
acquisition proposals and could delay or prevent a change in control of our
company. Such provisions may also have the effect of preventing changes in our
management.
 
    DELAWARE ANTI-TAKEOVER STATUTE
 
    We are subject to Section 203 of the Delaware General Corporation Law
("Section 203") which, subject to certain exceptions, prohibits a Delaware
corporation from engaging in any business combination with any interested
stockholder -- defined as any person or entity that is the beneficial
 
                                       71
<PAGE>
owner of at least 15% of a corporation's voting stock -- for a period of three
years following the time that such stockholder became an interested stockholder,
unless:
 
    - prior to such time, such corporation's board of directors approved either
      the business combination or the transaction that resulted in the
      stockholder becoming an interested stockholder;
 
    - upon consummation of the transaction that resulted in the stockholder
      becoming an interested stockholder, the interested stockholder owned at
      least 85% of such corporation's voting stock outstanding at the time the
      transaction commenced, excluding, for purposes of determining the number
      of shares outstanding, those shares owned (x) by persons who are directors
      and also officers and (y) by employee stock plans in which employee
      participants do not have the right to determine confidentially whether
      shares held subject to the plan will be tendered in a tender or exchange
      offer; or
 
    - at or subsequent to such time, the business combination is approved by
      such corporation's board of directors and authorized at an annual or
      special meeting of stockholders, and not by written consent, by the
      affirmative vote of at least two-thirds of the outstanding voting stock
      that is not owned by the interested stockholder.
 
    Section 203 defines business combination to include:
 
    - any merger or consolidation involving the corporation and the interested
      stockholder;
 
    - any sale, lease, exchange, mortgage, transfer, pledge or other disposition
      involving the interested stockholder and 10% or more of the assets of the
      corporation;
 
    - subject to certain exceptions, any transaction which results in the
      issuance or transfer by the corporation of any stock of the corporation to
      the interested stockholder;
 
    - any transaction involving the corporation that has the effect of
      increasing the proportionate share of the stock of any class or series of
      the corporation beneficially owned by the interested stockholder; or
 
    - the receipt by the interested stockholder of the benefit of any loans,
      advances, guarantees, pledges or other financial benefits provided by or
      through the corporation.
 
    RIGHTS PLAN
 
    Our Board of Directors has adopted a rights plan (the "Rights Agreement")
pursuant to which one right (a "Right") to purchase one one-thousandth of a
share (a "Unit") of a series of preferred stock, par value $0.001 per share (the
"Rights Plan preferred stock") at $115 per Unit was issued as a dividend for
each outstanding share of common stock. The Rights would become exercisable ten
days after a person or group acquires 15% or more of the outstanding common
stock or commences or announces a tender or exchange offer which would result in
such ownership.
 
    If, after the Rights become exercisable, we were to be acquired through a
merger or other business combination transaction or 50% or more of our assets or
earning power were sold, each Right would permit the holder to purchase, for the
exercise price, common stock of the acquiring company having a market value of
twice the exercise price. In addition, if any person acquires 15% or more of the
outstanding common stock, each Right not owned by such person would permit the
purchase, for the exercise price, of common stock having a market value of twice
the exercise price.
 
    The Rights expire on April 2, 2009, unless earlier redeemed by us in
accordance with the terms of the Rights Agreement. The purchase price payable
and the shares of Rights Plan preferred stock issuable upon exercise of the
Rights would be subject to adjustment from time to time as specified in the
Rights Agreement. In addition, our Board of Directors would retain the authority
to redeem, at
 
                                       72
<PAGE>
$0.001 per Right, and replace the Rights with new rights at any time, provided
that no such redemption could occur after a person or group acquires 15% or more
of the outstanding common stock.
 
    Shares of Rights Plan preferred stock, when issued upon exercise of the
Rights, will be nonredeemable and will rank junior to all series of any other
class of preferred stock. Each share of Rights Plan preferred stock will be
entitled to a cumulative preferential quarterly dividend payment equal to the
greater of (1) $115 per share or (2) 1,000 times the dividend declared per share
of common stock. In the event of liquidation, the holders of shares of Rights
Plan preferred stock will be entitled to a preferential liquidation payment
equal to the greater of (a) $1,000 per share or (b) 1,000 times the payment made
per share of common stock. Each share of Rights Plan preferred stock will
entitle the holder to 1,000 votes, voting together with the common stock.
Finally, in the event of any merger, consolidation or other transaction in which
common stock is exchanged, each share of Rights Plan preferred stock will be
entitled to receive 1,000 times the amount received per share of common stock.
The foregoing rights would be subject to antidilution adjustments. The number of
shares constituting the series of Rights Plan preferred stock will be 1,000,000.
 
TRANSFER AGENT AND REGISTRAR
 
    The transfer agent and registrar for the common stock is American Securities
Transfer & Trust, Inc.
 
                                       73
<PAGE>
                        SHARES ELIGIBLE FOR FUTURE SALE
 
    The market price of our common stock could decline as a result of sales of a
large number of shares of our common stock in the market after this offering, or
the perception that such sales could occur. Such sales also might make it more
difficult for us to sell equity securities in the future at a time and price
that we deem appropriate. After this offering, 70,564,582 shares of common stock
will be outstanding, and 456,595 shares will be held as treasury stock. Of the
70,564,582 outstanding shares, the 9,375,000 shares being offered hereby are
freely tradable. This leaves 61,189,582 shares eligible for sale in the public
market as follows:
 
<TABLE>
<CAPTION>
NUMBER OF SHARES   DATE
- -----------------  -----------------------------------------------------------------------------------------------
<S>                <C>
      1,120,047    After the date of this prospectus
        204,000    At various times after 90 days from the date of this prospectus (Rule 144)
     59,865,535    At various times after 180 days from the date of this prospectus (subject, in some cases, to
                     volume limitations) (lock-up and Rule 144)
</TABLE>
 
    In general, under Rule 144, as currently in effect, an affiliate of Rhythms
or a person (or persons whose shares are required to be aggregated) who has
beneficially owned shares for at least one year is entitled to sell, within any
three-month period, a number of shares that does not exceed the greater of (1)
1% of the then outstanding shares of common stock (approximately 710,212 shares
immediately after this offering) or (2) the average weekly trading volume in the
common stock during the four calendar weeks preceding the date on which notice
of such sale is filed, subject to certain restrictions. In addition, a person
who is not deemed to have been our affiliate at any time during the 90 days
preceding a sale, and who has beneficially owned the shares proposed to be sold
for at least two years, would be entitled to sell such shares under Rule 144(k)
without regard to the requirements described above. To the extent that shares
were acquired from one of our affiliates, such person's holding period for the
purpose of effecting a sale under Rule 144 commences on the date of transfer
from the affiliate. Securities issued in reliance on Rule 701 (such as shares of
common stock that may be acquired pursuant to the exercise of certain options
granted prior to this offering) are also restricted securities and may be sold
by stockholders other than our affiliates subject only to the manner of sale
provisions of Rule 144 and by our affiliates under Rule 144 without compliance
with its one-year holding period requirement.
 
    As of the date of this prospectus, options to purchase a total of 3,649,130
shares of common stock are outstanding and immediately exercisable, of which
3,840 shares are currently vested. Shares issued upon the exercise of stock
options granted under our stock option plans will be eligible for resale in the
public market from time to time subject to vesting and, in the case of certain
options, the expiration of the lock-up agreements referred to below.
 
    Our directors and officers and certain of our stockholders who beneficially
own 59,865,535 shares in the aggregate have entered into lock-up agreements
pursuant to which they have agreed that they will not offer, sell, or otherwise
dispose, directly or indirectly, any shares of common stock without the prior
written consent of Merrill Lynch and Salomon Smith Barney for a period of 180
days from the date of this prospectus.
 
    Warrants to purchase 7,184,674 shares of common stock will be outstanding
after this offering. The shares underlying these warrants will be eligible for
sale at various times after 180 days from the date of this prospectus. Certain
holders of warrants to purchase approximately 5,427,678 shares of common stock
have the right, subject to certain conditions and limitations, to include their
shares in certain registration statements relating to our securities. By
exercising their registration rights and causing a large number of shares to be
registered and sold in the public market, these holders may cause the price of
the common stock to fall. In addition, any demand to include such shares in our
registration statements could have an adverse effect on our ability to raise
needed capital. Please see "Business-- Legal Proceedings," "Management--Benefit
Plans," "Principal Stockholders," "Description of Capital Stock--Registration
Rights" and "Underwriting."
 
                                       74
<PAGE>
                                  UNDERWRITING
 
    Merrill Lynch, Pierce, Fenner & Smith Incorporated, Salomon Smith Barney
Inc., Hambrecht & Quist LLC and Thomas Weisel Partners LLC are acting as
representatives of the underwriters. Subject to the terms and conditions
contained in a purchase agreement, we have agreed to sell to each underwriter,
and each underwriter severally has agreed to purchase from us, the numbers of
shares of common stock set forth opposite its name below. The underwriters are
committed to purchase and pay for all such shares if any are purchased.
 
<TABLE>
<CAPTION>
                                                                   NUMBER OF
UNDERWRITER                                                         SHARES
- ----------------------------------------------------------------  -----------
<S>                                                               <C>
Merrill Lynch, Pierce, Fenner & Smith
          Incorporated..........................................   2,691,550
Salomon Smith Barney Inc. ......................................   2,691,550
Hambrecht & Quist LLC...........................................   1,177,200
Thomas Weisel Partners LLC......................................   1,177,200
BT Alex. Brown Incorporated.....................................     170,000
BancBoston Robertson Stephens Inc...............................     170,000
ING Baring Furman Selz LLC......................................     170,000
Janco Partners, Inc.............................................     170,000
Kirkpatrick, Pettis, Smith, Polian Inc..........................     170,000
First Albany Corporation........................................      87,500
Jefferies & Company, Inc........................................      87,500
Gerard Klauer Mattison & Co., Inc...............................      87,500
Ladenburg Thalmann & Co. Inc....................................      87,500
Legg Mason Wood Walker, Incorporated............................      87,500
Brad Peery Inc..................................................      87,500
Ragen MacKenzie Incorporated....................................      87,500
Raymond James & Associates, Inc.................................      87,500
Utendahl Capital Partners, L.P..................................      87,500
                                                                  -----------
          Total.................................................   9,375,000
                                                                  -----------
                                                                  -----------
</TABLE>
 
    The representatives have advised us that the underwriters propose to offer
the common stock to the public at the initial public offering price set forth on
the cover page of this prospectus and to certain dealers at such price less a
concession of not in excess of $.83 per share. The underwriters may allow, and
such dealers may reallow, a discount not in excess of $.10 per share to certain
other dealers. After the initial public offering, the public offering price,
concession and discount may be changed. No such change shall reduce the amount
of proceeds to be received by us as set forth on the cover page of this
prospectus.
 
    We have granted to the underwriters an option, exercisable during the 30-day
period after the date of this prospectus, to purchase up to 1,406,250 additional
shares of common stock, at the price set forth on the cover page of this
prospectus, less the underwriting discount. To the extent that the underwriters
exercise such option, each of the underwriters will have a firm commitment to
purchase approximately the same percentage of such additional shares that the
number of shares of common stock to be purchased by it shown in the above table
represents as a percentage of the 9,375,000 shares offered hereby. If purchased,
such additional shares will be sold by the underwriters on the same terms as
those on which the 9,375,000 shares are being sold.
 
                                       75
<PAGE>
    The purchase agreement contains covenants of indemnity among the
underwriters and us against certain civil liabilities, including liabilities
under the Securities Act and liabilities arising from breaches of
representations and warranties contained in the purchase agreement.
 
    The following table shows the per share and total underwriting discount we
will pay to the underwriters. The amounts are shown assuming both no exercise
and full exercise of the underwriters' option to purchase 1,406,250 additional
shares of common stock.
 
<TABLE>
<CAPTION>
                                                                                      TOTAL           TOTAL
                                                                      PER SHARE   WITHOUT OPTION   WITH OPTION
                                                                     -----------  --------------  --------------
<S>                                                                  <C>          <C>             <C>
Public Offering Price..............................................       $21.00    $196,875,000    $226,406,250
Underwriting Discount..............................................     $1.39125     $13,042,969     $14,999,414
Proceeds, before expenses, to Rhythms..............................    $19.60875    $183,832,031    $211,406,836
</TABLE>
 
    We expect to incur expenses of approximately $1.55 million in connection
with this offering.
 
    The common stock is being offered by the underwriters, subject to prior
sale, when, as and if issued to and accepted by them, subject to approval of
certain conditions by counsel to the underwriters and certain other conditions.
The underwriters reserve the right to withdraw, cancel or modify such offer and
to reject orders in whole or in part.
 
    Each of our officers and directors and substantially all of the holders of
common stock have agreed with the representatives, for a period of 180 days
after the date of this prospectus (the "Lock-Up Period"), subject to certain
exceptions, not to offer to sell, contract to sell, or otherwise sell, dispose
of, loan, pledge or grant any rights with respect to any shares of common stock,
any options or warrants to purchase any shares of common stock, or any
securities convertible into or exchangeable for shares of common stock owned as
of the date of this prospectus or thereafter acquired directly by such holders
or with respect to which they have or hereafter acquire the power of
disposition, without the prior written consent of Merrill Lynch and Salomon
Smith Barney. However, Merrill Lynch and Salomon Smith Barney may, in their sole
discretion and at any time without notice, release all or any portion of the
securities subject to lock-up agreements. We have agreed that during the Lock-Up
Period, we will not, subject to certain exceptions, without the prior written
consent of Merrill Lynch and Salomon Smith Barney, issue, sell, contract to sell
or otherwise dispose of, any shares of common stock, any options or warrants to
purchase any shares of common stock or any securities convertible into,
exercisable for or exchangeable for shares of common stock, other than the sale
of our shares in this offering, the issuance of common stock upon the exercise
of outstanding options and warrants and our issuance of options and stock under
the 1997 Stock Plan. See "Shares Eligible for Future Sale."
 
    The representatives have advised us that they do not intend to confirm sales
to any accounts over which they exercise discretionary authority.
 
    Prior to this offering, there has been no public market for our common
stock. Consequently, the initial public offering price for the common stock
offered hereby will be determined through negotiations between us and the
representatives. Among the factors to be considered in such negotiations are
prevailing market conditions, our financial information, market valuations of
other companies that we and the representatives believe to be comparable to us,
estimates of our business potential, the present state of our development and
other factors deemed relevant.
 
    Certain persons participating in this offering may engage in transactions,
including syndicate covering transactions or the imposition of penalty bids,
which may involve the purchase of common stock on the Nasdaq National Market or
otherwise. Such transactions may stabilize or maintain the market price of the
common stock at a level above that which might otherwise prevail in the open
market and, if commenced, may be discontinued at any time.
 
                                       76
<PAGE>
    The representatives have advised us that, pursuant to Regulation M under the
Securities Act, certain persons participating in this offering may engage in
transactions, including stabilizing bids, syndicate covering transactions or the
imposition of penalty bids, which may have the effect of stabilizing or
maintaining the market price of the common stock at a level above that which
might otherwise prevail in the open market. A "stabilizing bid" is a bid for or
the purchase of the common stock on behalf of the underwriters for the purpose
of fixing or maintaining the price of the common stock. A "syndicate covering
transaction" is the bid for or the purchase of the common stock on behalf of the
underwriters to reduce a short position incurred by the underwriters in
connection with the offering. A "penalty bid" is an arrangement permitting the
representatives to reclaim the selling concession otherwise accruing to an
underwriter or syndicate member in connection with this offering if the common
stock originally sold by such underwriter or syndicate member is purchased by
the representatives in a syndicate covering transaction and has therefore not
been effectively placed by such underwriter or syndicate member. The
representatives have advised us that such transactions may be effected on the
Nasdaq National Market or otherwise and, if commenced, may be discontinued at
any time.
 
    Merrill Lynch acted as an initial purchaser of our senior discount notes in
May 1998, for which it received usual and customary fees.
 
    Thomas Weisel Partners LLC was formed in October 1998.
 
                                 LEGAL MATTERS
 
    Brobeck, Phleger & Harrison LLP ("BPH"), San Diego, California, will pass
upon the validity of the issuance of the shares of common stock offered hereby
for us. Baker & McKenzie, New York, New York, will pass upon certain legal
matters related to the issuance of the shares of common stock offered hereby for
the underwriters. The BPH investment fund and certain BPH attorneys hold in the
aggregate 30,000 shares of Series A preferred stock which will convert into
72,000 shares of common stock upon the closing of this offering.
 
                                    EXPERTS
 
    The financial statements of the Company as of December 31, 1997 and 1998,
for the period from February 27, 1997 through December 31, 1997 and for the year
ended December 31, 1998, included in this prospectus, have been included herein
in reliance on the report of PricewaterhouseCoopers LLP, independent
accountants, given on the authority of that firm as experts in accounting and
auditing.
 
                      WHERE YOU CAN FIND MORE INFORMATION
 
    We have filed with the SEC a registration statement on Form S-1 under the
Securities Act with respect to the common stock. This prospectus does not
contain all of the information contained in the registration statement, and the
exhibits and schedules to the registration statement. For further information
with respect to us and our common stock, we refer you to the registration
statement, and the exhibits and schedules filed as part of the registration
statement. Statements in this prospectus concerning the contents of any contract
or any other document are not necessarily complete. If a contract or document
has been filed as an exhibit to the registration statement, we refer you to that
exhibit. Each statement in this prospectus relating to a contract or document
filed as an exhibit to the registration statement is qualified by the filed
exhibits.
 
    IN ADDITION, WE FILE REPORTS, PROXY STATEMENTS AND OTHER INFORMATION WITH
THE SEC. YOU MAY READ AND COPY ANY DOCUMENT WE FILE, INCLUDING THE REGISTRATION
STATEMENT, AT THE SEC'S PUBLIC REFERENCE ROOMS IN WASHINGTON, D.C., NEW YORK,
NEW YORK AND CHICAGO, ILLINOIS. PLEASE CALL THE SEC AT 1-800-SEC-0330 FOR
FURTHER INFORMATION ON THE PUBLIC REFERENCE ROOMS. OUR SEC FILINGS ARE ALSO
AVAILABLE TO THE PUBLIC ON THE SEC'S WEBSITE AT HTTP://WWW.SEC.GOV.
 
                                       77
<PAGE>
                               GLOSSARY OF TERMS
 
<TABLE>
<S>                            <C>
Asynchronous Transfer Mode...  High bandwidth, low-delay, connection-oriented, packet-like
                               switching and multiplexing technique requiring 53-byte,
                               fixed-sized cells.
 
Backbone.....................  An element of the network infrastructure that provides
                               high-speed, high capacity connections among the network's
                               physical points of presence, i.e., connection points and
                               Metro Service Centers. The backbone is used to transport end
                               user traffic across the metropolitan area and across the
                               United States.
 
Bandwidth....................  Refers to the maximum amount of data that can be transferred
                               through a computer's backbone or communication channel in a
                               given time. It is usually measured in Hertz, cycles per
                               second, for analog communications and bits per second for
                               digital communications.
 
Central Office...............  Incumbent carrier facility where subscriber lines are joined
                               to ILEC switching equipment.
 
Collocation..................  A location where a competitive carrier network interconnects
                               with the network of an incumbent carrier inside an incumbent
                               carrier's central office.
 
Competitive Carrier..........  Category of telephone service provider, or carrier, that
                               offers local exchange and other services similar to and in
                               competition with those of the incumbent carrier, as allowed
                               by recent changes in telecommunications law and regulation. A
                               competitive carrier may also provide other types of services
                               such as long distance telephone, data communications,
                               Internet access and video.
 
Copper Line or Loop..........  A pair of traditional copper telephone lines using electric
                               current to carry signals.
 
Digital......................  Describes a method of storing, processing and transmitting
                               information through the use of distinct electronic or optical
                               pulses that represent the binary digits 0 and 1. Digital
                               transmission and switching technologies employ a sequence of
                               these pulses to convey information, as opposed to the
                               continuously variable analog signal. The precise digital
                               numbers preclude distortion, such as graininess or "snow", in
                               the case of video transmission, or static or other background
                               distortion in the case of audio transmission.
 
Downstream...................  Refers to the transmission speed of a connection between our
                               connection point and the end user.
 
DS-0.........................  DIGITAL SERVICE 0. Standard telecommunications industry
                               digital signal format, which is distinguishable by bit rate
                               -- the number of binary digits transmitted per second. DS-0
                               service has a bit rate of 64 Kilobits per second.
 
DS-1.........................  DIGITAL SERVICE 1. In the digital hierarchy, this signaling
                               standard defines a transmission speed of 1.544 Mbps.
 
DS-3.........................  DIGITAL SERVICE 3. In the digital hierarchy, this signaling
                               standard defines a transmission speed of 44.736 Mbps,
                               equivalent to 28 T-1 channels. This term is often used
                               interchangeably with T-3.
</TABLE>
 
                                      A-1
<PAGE>
<TABLE>
<S>                            <C>
DSL..........................  DIGITAL SUBSCRIBER LINE. A transmission technology enabling
                               high-speed access in the local copper loop, often referred to
                               as the last mile between the network service provider --
                               I.E., an incumbent carrier, competitive carrier or an
                               internet service provider -- and end user.
 
E-Commerce...................  ELECTRONIC COMMERCE. An Internet service that supports
                               electronic transactions between customers and vendors to
                               purchase goods and services.
 
Encryption...................  Applying a specific algorithm to data so as to alter the
                               data's appearance and prevent other devices from reading the
                               information. Decryption applies the algorithm in reverse to
                               restore the data to its original form.
 
Firewall.....................  A computer device that separates a local area network from a
                               wide area network and prevents unauthorized access to the
                               local area network through the use of electronic security
                               mechanisms.
 
Frame Relay..................  A form of packet switching with variable length frames that
                               may be used with a variety of communications protocols.
 
Incumbent Carrier............  A company providing local exchange services on the date of
                               enactment of the Telecommunications Act of 1996. These
                               companies consist of the Regional Bell Operating Companies,
                               GTE and numerous independent telephone companies.
 
Interconnection Agreement....  A contract between an incumbent carrier and a competitive
                               carrier for the connection of a competitive carrier network
                               to the public switched telephone network, as well as
                               competitive carrier access to incumbent carrier unbundled
                               network elements, e.g., copper loops. This agreement sets out
                               some of the financial agreement and operational aspects of
                               such interconnection and access.
 
Internet.....................  An array of interconnected networks using a common set of
                               protocols defining the information coding and processing
                               requirements that can communicate across hardware platforms
                               and over many links; now operated by a consortium of
                               telecommunications service providers and others.
 
Internet Protocol............  A standard for software that keeps track of the inter-network
                               addresses for different nodes, routes outgoing messages and
                               recognizes incoming messages.
 
ISDN.........................  INTEGRATED SERVICES DIGITAL NETWORK. A transmission method
                               that provides circuit-switched access to the public network
                               at speeds of 64 or 128 Kbps for voice, data and video
                               transmission.
 
Internet Service Provider....  A company that provides direct access to the Internet.
 
Interexchange Carrier........  Usually referred to as a long-distance service provider.
                               There are many interexchange carriers, including AT&T, MCI
                               WorldCom, Sprint and Qwest.
 
Kbps.........................  KILOBITS PER SECOND. 1,000 bits per second.
</TABLE>
 
                                      A-2
<PAGE>
<TABLE>
<S>                            <C>
Long Distance Carrier........  A long distance carrier providing services between local
                               exchanges on an intrastate or interstate basis, also referred
                               to in the industry as an "interexchange carrier". A long
                               distance carrier may also be a long distance resale company.
 
Mbps.........................  MEGABITS PER SECOND. Millions of bits per second.
 
Modem........................  An abbreviation of Modulator-Demodulator. An electronic
                               signal-conversion device used to convert digital signals from
                               a computer to analog form for transmission over the telephone
                               network. At the transmitting end, a modem working as a
                               modulator converts the computer's digital signals into analog
                               signals that can be transmitted over a telephone line. At the
                               receiving end, another modem working as a demodulator
                               converts analog signals back into digital signals and sends
                               them to the receiving computer.
 
Multiplexing.................  An electronic or optical process that combines several lower
                               speed transmission signals into one higher speed signal.
 
Network......................  An integrated system composed of switching equipment and
                               transmission facilities designed to provide for the
                               direction, transport and recording of telecommunications
                               traffic.
 
OC-3.........................  OPTICAL CARRIER 3. Standard telecommunications industry
                               digital single format, which is distinguishable by bit rate
                               -- the number of binary digits transmitted per second. OC-3
                               service has a bit rate of 155.5 Mbps.
 
OC-12........................  OPTICAL CARRIER 12. Standard telecommunications industry
                               digital single format, which is distinguishable by bit rate
                               -- the number of binary digits transmitted per second. OC-12
                               service has a bit rate of 622.8 Mbps.
 
Packets......................  Information represented as bytes grouped together through a
                               communication node with a common destination address and
                               other attribute information.
 
Resellers....................  Generally used to refer to a telecommunications provider who
                               does not own any switching or transmission facilities. In
                               reality, a large number of providers furnish services through
                               a combination of owned and resold facilities.
 
Router.......................  A device that accepts the Internet Protocol from a local area
                               network or another wide area network device and
                               switches/routes Internet Protocol packets across a network
                               backbone. Routers also provide protocol conversion services
                               to transfer Internet Protocol packets over frame relay,
                               Asynchronous Transfer Mode, and other backbone network
                               services.
 
T-1..........................  This is a Bell System term for a digital transmission link
                               with a capacity of 1.544 Mbps.
 
TCP/IP.......................  TRANSMISSION CONTROL PROTOCOL/INTERNET PROTOCOL. A set of
                               network protocols that allow computers with different
                               architectures and operating system software to communicate
                               with other computers on the Internet.
 
Upstream.....................  Refers to the transmission speed of a connection between the
                               end user and our connection point.
</TABLE>
 
                                      A-3
<PAGE>
                          RHYTHMS NETCONNECTIONS INC.
                         INDEX TO FINANCIAL STATEMENTS
 
<TABLE>
<S>                                                                                    <C>
Report of Independent Accountants....................................................        F-2
 
Financial Statements:
 
  Consolidated Balance Sheets........................................................        F-3
 
  Consolidated Statements of Operations..............................................        F-4
 
  Consolidated Statements of Cash Flows..............................................        F-5
 
  Consolidated Statement of Stockholders' Equity.....................................        F-6
 
  Notes to Consolidated Financial Statements.........................................        F-7
</TABLE>
 
                                      F-1
<PAGE>
                       REPORT OF INDEPENDENT ACCOUNTANTS
 
To the Board of Directors and Stockholders
of Rhythms NetConnections Inc.
 
    In our opinion, the accompanying consolidated balance sheets and the related
consolidated statements of operations, of cash flows, and of stockholders'
equity present fairly, in all material respects, the financial position of
Rhythms NetConnections Inc. and subsidiaries at December 31, 1997 and 1998, and
the results of their operations and their cash flows for the period from
February 27, 1997 (inception) through December 31, 1997 and for the year ended
December 31, 1998 in conformity with generally accepted accounting principles.
These financial statements are the responsibility of the Company's management;
our responsibility is to express an opinion on these financial statements based
on our audits. We conducted our audits of these statements in accordance with
generally accepted auditing standards which require that we plan and perform the
audit to obtain reasonable assurance about whether the financial statements are
free of material misstatement. An audit includes examining, on a test basis,
evidence supporting the amounts and disclosures in the financial statements,
assessing the accounting principles used and significant estimates made by
management, and evaluating the overall financial statement presentation. We
believe that our audits provide a reasonable basis for the opinion expressed
above.
 
PRICEWATERHOUSECOOPERS LLP
 
Denver, Colorado
March 4, 1999, except for the last paragraph of Note 11
as to which the date is March 19, 1999
 
                                      F-2
<PAGE>
                          RHYTHMS NETCONNECTIONS INC.
 
                          CONSOLIDATED BALANCE SHEETS
 
<TABLE>
<CAPTION>
                                                                                    DECEMBER 31,    DECEMBER 31,
                                                                                        1997            1998
                                                                                    -------------  --------------
<S>                                                                                 <C>            <C>
                                                     ASSETS
 
Current assets:
  Cash and cash equivalents.......................................................  $  10,166,000  $   21,315,000
  Short-term investments..........................................................       --           115,497,000
  Accounts, loans and other receivables, net......................................       --             2,376,000
  Inventory.......................................................................       --               340,000
  Prepaid expenses and other current assets.......................................         95,000         230,000
                                                                                    -------------  --------------
  Total current assets............................................................     10,261,000     139,758,000
Equipment and furniture, net......................................................      1,621,000      11,510,000
Collocation fees, net.............................................................        327,000      13,804,000
Deferred debt issue costs, net....................................................       --             6,304,000
Other assets......................................................................         32,000         350,000
                                                                                    -------------  --------------
                                                                                    $  12,241,000  $  171,726,000
                                                                                    -------------  --------------
                                                                                    -------------  --------------
 
                                      LIABILITIES AND STOCKHOLDERS' EQUITY
 
Current liabilities:
  Current portion of long-term debt...............................................  $     126,000  $      333,000
  Accounts payable................................................................        951,000      10,601,000
  Accrued expenses and other current liabilities..................................        376,000       2,855,000
                                                                                    -------------  --------------
    Total current liabilities.....................................................      1,453,000      13,789,000
Long-term debt....................................................................        442,000         472,000
13.5% senior discount notes, net..................................................       --           157,465,000
Other liabilities.................................................................       --               180,000
                                                                                    -------------  --------------
    Total liabilities.............................................................      1,895,000     171,906,000
                                                                                    -------------  --------------
Commitments (note 10)
Mandatorily redeemable common stock warrants......................................       --             6,567,000
                                                                                    -------------  --------------
Stockholders' equity (deficit):
  Series A convertible preferred stock, $0.001 par value; 17,000,000 shares
    authorized in 1997, 12,900,000 shares in 1998; 12,490,000 shares issued and
    outstanding in 1997, 12,855,094 shares in 1998................................         12,000          13,000
  Series B convertible preferred stock, $0.001 par value; no shares authorized in
    1997, 4,044,943 shares in 1998; no shares issued and outstanding in 1997,
    4,044,943 shares in 1998......................................................       --                 4,000
  Common stock, $0.001 par value; 54,635,294 shares authorized in 1997, 80,049,892
    shares in 1998; 2,482,222 shares issued in 1997, 8,042,530 shares in 1998.....          2,000           8,000
  Treasury stock, at cost; 438,115 shares.........................................       --               (18,000)
  Additional paid-in capital......................................................     14,012,000      37,212,000
  Deferred compensation...........................................................     (1,258,000)     (5,210,000)
  Accumulated deficit.............................................................     (2,422,000)    (38,756,000)
                                                                                    -------------  --------------
    Total stockholders' equity (deficit)..........................................     10,346,000      (6,747,000)
                                                                                    -------------  --------------
                                                                                    $  12,241,000  $  171,726,000
                                                                                    -------------  --------------
                                                                                    -------------  --------------
</TABLE>
 
   The accompanying notes are an integral part of these financial statements.
 
                                      F-3
<PAGE>
                          RHYTHMS NETCONNECTIONS INC.
 
                     CONSOLIDATED STATEMENTS OF OPERATIONS
 
<TABLE>
<CAPTION>
                                                                             PERIOD FROM
                                                                          FEBRUARY 27, 1997
                                                                             (INCEPTION)
                                                                               THROUGH           YEAR ENDED
                                                                          DECEMBER 31, 1997   DECEMBER 31, 1998
                                                                          ------------------  -----------------
<S>                                                                       <C>                 <C>
Revenue:
  Service and installation, net.........................................    $     --           $       528,000
                                                                          ------------------  -----------------
Operating Expenses:
  Network and service costs.............................................          --                 4,695,000
  Selling and marketing.................................................            33,000           3,776,000
  General and administrative............................................         2,501,000          19,377,000
  Depreciation and amortization.........................................             1,000           1,081,000
                                                                          ------------------  -----------------
    Total operating expenses............................................         2,535,000          28,929,000
                                                                          ------------------  -----------------
Loss from Operations....................................................        (2,535,000)        (28,401,000)
                                                                          ------------------  -----------------
Other Income and Expense:
  Interest income.......................................................           114,000           5,813,000
  Interest expense (including amortized debt discount and issue
    costs)..............................................................            (1,000)        (13,779,000)
  Other.................................................................          --                    33,000
                                                                          ------------------  -----------------
Net Loss................................................................    $   (2,422,000)    $   (36,334,000)
                                                                          ------------------  -----------------
                                                                          ------------------  -----------------
Net Loss Per Share:
  Basic.................................................................    $        (1.12)    $        (12.18)
                                                                          ------------------  -----------------
                                                                          ------------------  -----------------
  Diluted...............................................................    $        (1.12)    $        (12.18)
                                                                          ------------------  -----------------
                                                                          ------------------  -----------------
Shares Used in Computing Net Loss Per Share:
  Basic.................................................................         2,161,764           2,984,216
                                                                          ------------------  -----------------
                                                                          ------------------  -----------------
  Diluted...............................................................         2,161,764           2,984,216
                                                                          ------------------  -----------------
                                                                          ------------------  -----------------
</TABLE>
 
   The accompanying notes are an integral part of these financial statements.
 
                                      F-4
<PAGE>
                          RHYTHMS NETCONNECTIONS INC.
 
                     CONSOLIDATED STATEMENTS OF CASH FLOWS
 
<TABLE>
<CAPTION>
                                                                                PERIOD FROM
                                                                             FEBRUARY 27, 1997
                                                                                (INCEPTION)
                                                                                  THROUGH           YEAR ENDED
                                                                             DECEMBER 31, 1997   DECEMBER 31, 1998
                                                                             ------------------  -----------------
<S>                                                                          <C>                 <C>
Cash Flows from Operating Activities:
  Net Loss.................................................................     $ (2,422,000)      $ (36,334,000)
  Adjustments to reconcile net loss to net cash used for operating
    activities:
    Depreciation of equipment and furniture................................            1,000             454,000
    Amortization of collocation fees.......................................          --                   85,000
    Amortization of debt discount and deferred debt issue costs............          --               13,882,000
    Amortization of deferred compensation..................................          192,000             725,000
    Compensation expense from stock option issued to employee..............           73,000            --
    Loss on sale of equipment to leasing company...........................          --                  387,000
    Changes in assets and liabilities:
      Increase in accounts, loans and other receivables, net...............          --               (2,376,000)
      Increase in inventory................................................          --                 (340,000)
      Increase in prepaid expenses and other current assets................          (95,000)           (135,000)
      Increase in other assets.............................................          (32,000)           (318,000)
      Increase in accounts payable.........................................          388,000           2,287,000
      Increase in accrued expenses and other current liabilities...........          335,000           2,479,000
      Increase in other liabilities........................................          --                  180,000
                                                                             ------------------  -----------------
    Net cash used for operating activities.................................       (1,560,000)        (19,024,000)
                                                                             ------------------  -----------------
Cash Flows from Investing Activities:
  Purchases of short-term investments......................................          --             (451,870,000)
  Maturities of short-term investments.....................................          --              336,373,000
  Purchases of equipment and furniture.....................................       (1,018,000)         (9,973,000)
  Payment of collocation fees..............................................         (327,000)        (13,562,000)
                                                                             ------------------  -----------------
    Net cash used for investing activities.................................       (1,345,000)       (139,032,000)
                                                                             ------------------  -----------------
Cash Flows from Financing Activities:
  Proceeds from leasing company for equipment..............................          --                6,606,000
  Proceeds from issuance of 13.5% senior discount notes and warrants.......          --              150,365,000
  Payment of debt issue costs on 13.5% senior discount notes...............          --               (6,519,000)
  Proceeds from borrowings on long-term debt...............................          568,000             432,000
  Repayments on long-term debt.............................................          --                 (195,000)
  Proceeds from issuance of common stock...................................           13,000             242,000
  Proceeds from issuance of preferred stock................................       12,490,000          18,292,000
  Purchase of treasury stock...............................................          --                  (18,000)
                                                                             ------------------  -----------------
    Net cash provided by financing activities..............................       13,071,000         169,205,000
                                                                             ------------------  -----------------
Net increase in cash and cash equivalents..................................       10,166,000          11,149,000
Cash and cash equivalents at beginning of period...........................          --               10,166,000
                                                                             ------------------  -----------------
Cash and cash equivalents at end of period.................................     $ 10,166,000       $  21,315,000
                                                                             ------------------  -----------------
                                                                             ------------------  -----------------
Supplemental schedule of cash flow information:
  Cash paid for interest...................................................     $      3,000       $      66,000
                                                                             ------------------  -----------------
                                                                             ------------------  -----------------
Supplemental schedule of non-cash financing activities:
  Equipment purchases payable, to be financed through operating leases.....     $    604,000       $    --
                                                                             ------------------  -----------------
                                                                             ------------------  -----------------
  Equipment and furniture purchases payable................................     $    --            $   7,363,000
                                                                             ------------------  -----------------
                                                                             ------------------  -----------------
</TABLE>
 
   The accompanying notes are an integral part of these financial statements.
 
                                      F-5
<PAGE>
                          RHYTHMS NETCONNECTIONS INC.
                 CONSOLIDATED STATEMENT OF STOCKHOLDERS' EQUITY
<TABLE>
<CAPTION>
                                               SERIES A            SERIES B
                                              CONVERTIBLE         CONVERTIBLE
                                            PREFERRED STOCK     PREFERRED STOCK     COMMON STOCK
                                           $0.001 PAR VALUE    $0.001 PAR VALUE   $0.001 PAR VALUE
                                          -------------------  -----------------  -----------------
                                           # SHARES   AMOUNT   # SHARES   AMOUNT  # SHARES   AMOUNT
                                          ----------  -------  ---------  ------  ---------  ------
<S>                                       <C>         <C>      <C>        <C>     <C>        <C>
Issuance of common stock to Founders (at
  inception)............................      --      $ --        --      $--     2,161,764  $2,000
Issuance of Series A preferred stock for
  cash ($1.00 per share)................  12,490,000  12,000      --       --        --       --
Issuance of common stock upon exercise
  of options ($0.04 per share exercise
  price)................................      --        --        --       --      320,458    --
Grant of options to purchase Series A
  preferred stock ($0.80 per share
  exercise price).......................      --        --        --       --        --       --
Deferred compensation from grants of
  options to purchase common stock......      --        --        --       --        --       --
Amortization of deferred compensation...      --        --        --       --        --       --
Net loss for 1997.......................      --        --        --       --        --       --
                                          ----------  -------  ---------  ------  ---------  ------
Balance at December 31, 1997............  12,490,000  12,000      --       --     2,482,222  2,000
Issuance of Series A preferred stock for
  cash ($0.80 per share)................     365,094   1,000      --       --        --       --
Issuance of Series B preferred stock for
  cash ($4.45 per share)................      --        --     4,044,943  4,000      --       --
Issuance of common stock upon exercise
  of options ($0.04 to $0.25 per share
  exercise price).......................      --        --        --       --     5,560,308  6,000
Purchase of treasury stock for cash
  ($0.04 per share).....................      --        --        --       --        --       --
Deferred compensation from grants of
  options to purchase common stock......      --        --        --       --        --       --
Amortization of deferred compensation...      --        --        --       --        --       --
Reversal of deferred compensation from
  cancellation of grants to purchase
  common stock..........................      --        --        --       --        --       --
Net loss for 1998.......................      --        --        --       --        --       --
                                          ----------  -------  ---------  ------  ---------  ------
Balance at December 31, 1998............  12,855,094  $13,000  4,044,943  $4,000  8,042,530  $8,000
                                          ----------  -------  ---------  ------  ---------  ------
                                          ----------  -------  ---------  ------  ---------  ------
 
<CAPTION>
 
                                            TREASURY STOCK                                                   TOTAL
                                                AT COST        ADDITIONAL                                STOCKHOLDERS'
                                          -------------------    PAID-IN      DEFERRED     ACCUMULATED      EQUITY
                                          # SHARES    AMOUNT     CAPITAL    COMPENSATION     DEFICIT       (DEFICIT)
                                          --------   --------  -----------  ------------   ------------  -------------
<S>                                       <C>        <C>       <C>          <C>            <C>           <C>
Issuance of common stock to Founders (at
  inception)............................    --       $  --     $   --       $   --         $   --         $     2,000
Issuance of Series A preferred stock for
  cash ($1.00 per share)................    --          --      12,477,000      --             --          12,489,000
Issuance of common stock upon exercise
  of options ($0.04 per share exercise
  price)................................    --          --          12,000      --             --              12,000
Grant of options to purchase Series A
  preferred stock ($0.80 per share
  exercise price).......................    --          --          73,000      --             --              73,000
Deferred compensation from grants of
  options to purchase common stock......    --          --       1,450,000   (1,450,000)       --             --
Amortization of deferred compensation...    --          --         --           192,000        --             192,000
Net loss for 1997.......................    --          --         --           --          (2,422,000 )   (2,422,000)
                                          --------   --------  -----------  ------------   ------------  -------------
Balance at December 31, 1997............    --          --      14,012,000   (1,258,000)    (2,422,000 )   10,346,000
Issuance of Series A preferred stock for
  cash ($0.80 per share)................    --          --         291,000      --             --             292,000
Issuance of Series B preferred stock for
  cash ($4.45 per share)................    --          --      17,996,000      --             --          18,000,000
Issuance of common stock upon exercise
  of options ($0.04 to $0.25 per share
  exercise price).......................    --          --         236,000      --             --             242,000
Purchase of treasury stock for cash
  ($0.04 per share).....................  438,115     (18,000)     --           --             --             (18,000)
Deferred compensation from grants of
  options to purchase common stock......    --          --       4,908,000   (4,908,000)       --             --
Amortization of deferred compensation...    --          --         --           725,000        --             725,000
Reversal of deferred compensation from
  cancellation of grants to purchase
  common stock..........................    --          --        (231,000)     231,000        --             --
Net loss for 1998.......................    --          --         --           --         (36,334,000 )  (36,334,000)
                                          --------   --------  -----------  ------------   ------------  -------------
Balance at December 31, 1998............  438,115    $(18,000) $37,212,000  $(5,210,000)   $(38,756,000)  $(6,747,000)
                                          --------   --------  -----------  ------------   ------------  -------------
                                          --------   --------  -----------  ------------   ------------  -------------
</TABLE>
 
   The accompanying notes are an integral part of these financial statements.
 
                                      F-6
<PAGE>
                          RHYTHMS NETCONNECTIONS INC.
 
                   NOTES TO CONSOLIDATED FINANCIAL STATEMENTS
 
NOTE 1--THE COMPANY
 
    Rhythms NetConnections Inc. (the "Company"), a Delaware corporation, was
organized under the name Accelerated Connections Inc. effective February 27,
1997. The Company's name was changed to Rhythms NetConnections Inc. as of August
15, 1997. The Company is in the business of providing high-speed data
communications services on an end-to end basis to business customers and end
users. The Company began service trials in the San Diego, California, market in
December 1997 and began commercial operations in San Diego effective April 1,
1998.
 
    The Company's ultimate success depends upon, among other factors, rapidly
expanding the geographic coverage of its network services; entering into
interconnection agreements with incumbent local exchange carriers, some of which
are competitors or potential competitors of the Company; deploying network
infrastructure; attracting and retaining customers; accurately assessing
potential markets; continuing to develop and integrate its operational support
system and other back office systems; obtaining any required governmental
authorizations; responding to competitive developments; continuing to attract,
retain and motivate qualified personnel; and continuing to upgrade its
technologies and commercialize its network services incorporating such
technologies. There can be no assurance that the Company will be successful in
addressing these matters and failure to do so could have a material adverse
effect on the Company's business, prospects, operating results and financial
condition. As the Company continues the development of its business, it will
seek additional sources of financing to fund its development. If unsuccessful in
obtaining such financing, the Company will continue expansion of its operations
on a reduced scale based on its existing capital resources.
 
NOTE 2--SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
 
    PRINCIPLES OF CONSOLIDATION:  The accompanying consolidated financial
statements include the transactions and balances of Rhythms NetConnections Inc.
and its wholly owned subsidiaries ACI Corp. and ACI Corp.--Virginia (since
February 1998). All material intercompany transactions and balances have been
eliminated.
 
    USE OF ESTIMATES:  The preparation of financial statements in conformity
with generally accepted accounting principles requires management to make
estimates and assumptions that affect the reported amounts of assets and
liabilities and the disclosure of contingent assets and liabilities at the
financial statement date, as well as the reported amounts of revenues and
expenses during the reporting period. Actual results could differ from those
estimates.
 
    REVENUE RECOGNITION:  Revenue is recorded in the period services are
provided to customers.
 
    CASH AND CASH EQUIVALENTS:  Cash and cash equivalents include cash on hand,
money market funds, certificates of deposit, obligations of the U.S. Government
and its agencies and commercial paper with a maturity of 90 days or less at the
time of purchase.
 
    SHORT-TERM INVESTMENTS.  Short-term investments consist of obligations of
the U.S. Government and its agencies and commercial paper that have an original
maturity between 91 days and one year from the date of purchase. Management
determines the appropriate classification of marketable debt and equity
securities at the time of purchase and reevaluates such designation as of each
balance sheet date.
 
    FAIR VALUE OF FINANCIAL INSTRUMENTS:  The carrying amounts of the Company's
financial instruments as presented are reasonable estimates of those
instruments' fair values because of the short maturity of
 
                                      F-7
<PAGE>
                          RHYTHMS NETCONNECTIONS INC.
 
             NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (CONTINUED)
 
NOTE 2--SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (CONTINUED)
those instruments or based on the current rates offered to the Company for debt
of the same remaining maturities.
 
    INVENTORY:  Inventory consists of communications equipment that will be
installed at customer locations. Inventory is accounted for on a FIFO basis at
the lower of cost or market.
 
    EQUIPMENT AND FURNITURE:  Equipment and furniture consists of purchased
equipment, furniture, computer software, and leasehold improvements. Equipment
and furniture is recorded at cost. Depreciation is computed using the
straight-line method over the estimated useful lives of the assets, generally
three to seven years or the lease term if shorter. When equipment and furniture
is retired, sold or otherwise disposed of, the cost and related accumulated
depreciation are removed from the accounts and gains and losses resulting from
such transactions are reflected in operations.
 
    COLLOCATION FEES:  Collocation fees represent nonrecurring fees paid to
secure Central Office space for location of certain Company equipment. The fees
are amortized over their estimated useful lives of ten years.
 
    IMPAIRMENT OF LONG-LIVED ASSETS:  The Company investigates potential
impairments of their long-lived assets on an exception basis when evidence
exists that events or changes in circumstances may have made recovery of an
asset's carrying value unlikely. An impairment loss is recognized when the sum
of the expected undiscounted future net cash flows is less than the carrying
amount of the asset. No such losses have been identified.
 
    CONCENTRATIONS OF CREDIT RISK:  Credit risk is primarily concentrated in
cash equivalents and short-term investments. Cash in excess of operating
requirements is conservatively invested in money market funds, certificates of
deposit with high-quality financial institutions, obligations of the U.S.
Government and its agencies and commercial paper rated A-1, P-1 to minimize
risk.
 
    Two customers comprise 14.9 percent and 7.5 percent of the Company's net
trade receivable balance at December 31, 1998 and 36.7 percent and 13.7 percent
of revenues for the year ended December 31, 1998.
 
    INCOME TAXES:  The Company provides for income taxes utilizing the liability
method. Under the liability method, current income tax expense or benefit
represents income taxes expected to be payable or refundable for the current
period. Deferred income tax assets and liabilities are established for both the
impact of differences between the financial reporting bases and tax bases of
assets and liabilities and for the expected future tax benefit to be derived
from tax credits and tax loss carryforwards. Deferred income tax expense or
benefit represents the change during the reporting period in the net deferred
income tax assets and liabilities. Deferred tax assets are reduced by a
valuation allowance when, in the opinion of management, it is more likely than
not that some portion or all of the deferred tax assets will not be realized.
 
    NET LOSS PER SHARE:  The Company has adopted Statement of Financial
Accounting Standard ("SFAS") No. 128, "Earnings Per Share." Basic earnings per
share ("EPS") is calculated by dividing the income or loss available to common
stockholders by the weighted average number of common shares outstanding for the
period, without consideration for common stock equivalents. Diluted EPS is
computed by dividing the income or loss available to common stockholders by the
weighted average number of common shares outstanding for the period in addition
to the weighted average number of
 
                                      F-8
<PAGE>
                          RHYTHMS NETCONNECTIONS INC.
 
             NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (CONTINUED)
 
NOTE 2--SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (CONTINUED)
common stock equivalents outstanding for the period. Shares subject to
repurchase by the Company are considered common stock equivalents for purposes
of this calculation. Shares issuable upon conversion of the Series A and Series
B preferred stock, upon the exercise of outstanding stock options and warrants
and shares issued subject to repurchase by the Company totaling 36,653,940 and
52,958,513 at December 31, 1997 and 1998, respectively, have been excluded from
the computation since their effect would be antidilutive.
 
    STOCK-BASED COMPENSATION:  The Company measures compensation expense for
their employee stock-based compensation using the intrinsic value method and
provides pro forma disclosures of net loss as if the fair value method had been
applied in measuring compensation expense. Under the intrinsic value method of
accounting for stock-based compensation, when the exercise price of options
granted to employees is less than the fair value of the underlying stock on the
date of grant, compensation expense is to be recognized over the applicable
vesting period.
 
    NEW ACCOUNTING PRONOUNCEMENTS:  In June 1998, SFAS No. 133, "Accounting for
Derivative Instruments and Hedging Activities," was issued. This statement
establishes accounting and reporting standards for derivative instruments and
for hedging activities. The Company will adopt SFAS No. 133 as required in 2000.
The Company expects that adoption will have no impact on their consolidated
financial statements.
 
    RECLASSIFICATIONS:  Certain 1997 balances have been reclassified to conform
to the 1998 presentation.
 
NOTE 3--SHORT-TERM INVESTMENTS
 
    The Company's marketable debt securities are classified as held-to-maturity
and carried at amortized cost, which approximates fair value. Short-term
investments consist of the following:
 
<TABLE>
<CAPTION>
                                                                 DECEMBER 31,   DECEMBER 31,
                                                                     1997           1998
                                                                 ------------  --------------
<S>                                                              <C>           <C>
Commercial Paper...............................................   $       --   $   33,170,000
U.S. Government Securities.....................................           --       82,327,000
                                                                 ------------  --------------
                                                                  $       --   $  115,497,000
                                                                 ------------  --------------
                                                                 ------------  --------------
</TABLE>
 
                                      F-9
<PAGE>
                          RHYTHMS NETCONNECTIONS INC.
 
             NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (CONTINUED)
 
NOTE 4--COMPOSITION OF CERTAIN BALANCE SHEET COMPONENTS
 
<TABLE>
<CAPTION>
                                                           DECEMBER 31,        DECEMBER 31,
                                                               1997                1998
                                                         -----------------  ------------------
<S>                                                      <C>                <C>
Accounts, loans and other receivables, net:
  Interest.............................................    $          --      $    2,135,000
  Trade, net of allowance for doubtful accounts of
    $50,000 in 1998....................................               --             197,000
  Employee expense advances and loans..................               --              44,000
                                                         -----------------  ------------------
                                                           $          --      $    2,376,000
                                                         -----------------  ------------------
                                                         -----------------  ------------------
 
Equipment and furniture, net:
  Operating equipment..................................    $   1,241,000      $    9,633,000
  Office furniture.....................................           43,000             917,000
  Leasehold improvements...............................           32,000             668,000
  Computer software....................................          173,000             456,000
  Computer equipment...................................          133,000             274,000
  Lab equipment........................................               --              17,000
  Accumulated depreciation.............................           (1,000)           (455,000)
                                                         -----------------  ------------------
                                                           $   1,621,000      $   11,510,000
                                                         -----------------  ------------------
                                                         -----------------  ------------------
 
Accrued expenses and other current liabilities:
  Accrued payroll......................................    $     217,000      $    1,524,000
  Carrier services and other operating costs...........               --             991,000
  Other................................................          159,000             340,000
                                                         -----------------  ------------------
                                                           $     376,000      $    2,855,000
                                                         -----------------  ------------------
                                                         -----------------  ------------------
</TABLE>
 
NOTE 5--DEBT
 
    As of December 31, 1997 and 1998, the Company had a note payable of $568,000
and $805,000, respectively, to a financial institution. Terms of the note
payable include an interest rate of prime plus 0.25 percent (8.75 percent and
8.0 percent at December 31, 1997 and 1998, respectively) payable monthly on the
outstanding principal. The note is collateralized by assets of the Company and
is to be amortized over a 36-month repayment period. The $805,000 will be repaid
during the years 1999 through 2001 in the amounts of $333,000 each in 1999 and
2000 and $139,000 in 2001.
 
    On May 5, 1998, the Company issued 13.5 percent senior discount notes due
2008 in the principal amount of $290,000,000 at maturity, combined with warrants
to purchase 4,732,800 shares of common stock. The notes were issued at a
discount; cash proceeds from the issuance of the notes and warrants were
$150,365,000. The Company additionally incurred approximately $6,519,000 in debt
issue costs. The notes will accrete in value through May 15, 2003 at a rate of
13.5 percent per annum, compounded semi-annually; no cash interest will be
payable prior to that date. Upon a change in control or upon certain asset
sales, the Company must offer to repurchase all or a portion of the outstanding
notes. In addition, the Company has the option to repurchase the notes upon
payment of a premium of accreted value at that point in time. The notes contain
covenants that restrict the Company's ability to make certain payments,
including dividend payments, and incur additional debt.
 
                                      F-10
<PAGE>
                          RHYTHMS NETCONNECTIONS INC.
 
             NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (CONTINUED)
 
NOTE 5--DEBT (CONTINUED)
    The warrants issued in connection with the senior discount notes are
exercisable at a price of $0.004 per share. The warrants expire May 15, 2008.
The warrants may be required to be repurchased by the Company for cash upon the
occurrence of a repurchase event, such as a consolidation, merger, or sale of
assets to another entity, as defined in the provisions of the Warrant Agreement,
at a price to be determined by an independent financial expert selected by the
Company. In the event a repurchase event occurs, the difference between the
repurchase price and the carrying value of the warrants would be charged to
equity. The value ascribed to the warrants of $6,567,000 resulted in additional
debt discount, which, together with the debt issue costs are being amortized to
interest expense using the effective interest method over the period that the
notes are outstanding.
 
    Effective November 20, 1998, the Company completed an exchange offer of the
13.5 percent senior discount notes that allowed for registration of such notes
under the Securities Act of 1933, as amended. $289,000,000 of the original issue
notes were tendered for exchange. The registered notes have substantially the
same terms and conditions as the unregistered notes, except that the registered
notes are not subject to the restrictions on resale or transfer that applied to
the unregistered notes.
 
    During May 1998 the Company entered into a 36-month lease line that provides
for $24.5 million in equipment on an operating lease basis. In connection with
this lease agreement, the Company issued 574,380 warrants to purchase common
stock at a price of $1.85 per share, exercisable immediately.
 
NOTE 6--STOCKHOLDERS' EQUITY
 
    The Company was initially capitalized in February 1997 with common stock. In
July 1997, the Company was granted authority to issue two classes of stock
consisting of up to 17,000,000 shares of Series A preferred stock and 54,635,294
shares of common stock, as adjusted for the November 1998 and March 1999 stock
splits, both with a $0.001 par value per share.
 
    Effective March 6, 1998, the Company amended its Certificate of
Incorporation to increase the number of authorized common shares to 54,983,160,
as adjusted for the November 1998 and March 1999 stock splits, to decrease the
number of authorized preferred shares to 16,944,943, and to designate 12,900,000
of the preferred shares as Series A and 4,044,943 shares as Series B.
 
    Effective April 28, 1998, the Company amended its Certificate of
Incorporation to increase the number of authorized common shares to 59,715,960,
as adjusted for the November 1998 and March 1999 stock splits.
 
    Effective November 4, 1998, the Company completed a two-for-one split of its
common stock. The accompanying consolidated financial statements have been
restated for all periods presented to reflect the stock split.
 
    The Company's Series A and Series B preferred stock may be converted, at the
option of the holder, into the Company's common stock on a 2.4 to 1 basis,
subject to antidilution protection on a broad-based weighted-average basis. The
preferred stock will also be automatically converted upon certain closings of
registered public offerings of common stock. The holders of the Series A
preferred stock are entitled to receive non-cumulative dividends in the amount
equal to $0.08 per share per annum and the holders of the Series B preferred
stock are entitled to receive non-cumulative dividends of $0.356 per share per
annum, as and if declared by the Board of Directors, or an amount equal to that
paid on any other outstanding shares of the Company, payable quarterly, as and
if declared by the Board of Directors. In the event of a liquidation of the
Company, the holders of the Series A and
 
                                      F-11
<PAGE>
                          RHYTHMS NETCONNECTIONS INC.
 
             NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (CONTINUED)
 
NOTE 6--STOCKHOLDERS' EQUITY (CONTINUED)
Series B preferred stock will be entitled, in preference to the holders of
common stock, to an amount equal to $1.00 per share and $4.45 per share,
respectively, plus all declared and unpaid dividends. The preferred shares
entitle holders to two votes per share, on an "as-converted" basis.
 
NOTE 7--STOCK OPTIONS
 
    The Company has established the 1997 Stock Option/Stock Issuance Plan (the
"Plan"), which provides for the grant of options to employees, directors and
outside consultants for purchase of up to an aggregate of 11,673,530 shares of
common stock. The options are immediately exercisable and expire within ten
years after the date of grant. Shares acquired upon exercise are subject to
repurchase by the Company ratably over a four-year period from the date of
grant, at the option of the Company and at the exercise price. The Plan provides
for both incentive option and non-statutory option grants and for accelerated
vesting in the event of a 50 percent or more change in control of the Company.
 
    Plan activity is as follows:
 
<TABLE>
<CAPTION>
                                                                   NUMBER OF   WEIGHTED AVERAGE   WEIGHTED AVERAGE
                                                                    SHARES        FAIR VALUE       EXERCISE PRICE
                                                                  -----------  -----------------  -----------------
<S>                                                               <C>          <C>                <C>
    Granted.....................................................    5,801,714      $    0.29          $    0.04
    Exercised...................................................     (320,458)     $    0.29          $    0.04
                                                                  -----------
        Outstanding at December 31, 1997........................    5,481,256      $    0.29          $    0.04
 
    Granted.....................................................    3,364,680      $    2.62          $    0.84
    Exercised...................................................   (5,560,308)     $    0.30          $    0.04
    Canceled....................................................     (136,348)     $    1.10          $    0.22
                                                                  -----------
 
        Outstanding at December 31, 1998........................    3,149,280      $    2.73          $    0.89
                                                                  -----------
                                                                  -----------
</TABLE>
 
    The following summarizes the outstanding and exercisable options under the
Plan at December 31, 1998:
 
<TABLE>
<CAPTION>
                                  WEIGHTED
                                   AVERAGE        WEIGHTED                    WEIGHTED
                     NUMBER       REMAINING        AVERAGE       NUMBER        AVERAGE
 EXERCISE PRICE    OUTSTANDING      LIFE       EXERCISE PRICE   EXERCISABLE EXERCISE PRICE
- -----------------  -----------  -------------  ---------------  ---------  ---------------
                                     OPTIONS OUTSTANDING           OPTIONS EXERCISABLE
<S>                <C>          <C>            <C>              <C>        <C>
                                ------------------------------  --------------------------
      $0.04           177,480    9.03 years       $    0.04       177,480     $    0.04
 $0.21 to $0.25     1,591,680    9.42 years       $    0.23     1,591,680     $    0.23
 $1.67 to $1.88     1,380,120    9.83 years       $    1.75     1,380,120     $    1.75
</TABLE>
 
    During 1997 and 1998, all options were granted to employees at less than
fair value on the date of grant, resulting in $1,450,000 and $4,908,000,
respectively, of deferred compensation recorded as a reduction of stockholders'
equity. These amounts are being amortized as a charge to general and
administrative expenses over the vesting periods of the applicable options; such
amortization totaled $192,000 and $725,000 for the periods ended December 31,
1997 and 1998, respectively.
 
    An option to purchase 365,094 shares of Series A Preferred Stock at $0.80
per share was granted to an employee during 1997. The Company recorded $73,000
in compensation expense during 1997 related to this grant.
 
                                      F-12
<PAGE>
                          RHYTHMS NETCONNECTIONS INC.
 
             NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (CONTINUED)
 
NOTE 7--STOCK OPTIONS (CONTINUED)
    Had compensation expense for the Company's Plan and the Preferred Stock
option been determined based on the fair value method of accounting for
stock-based compensation, the Company's net loss and net loss per share for the
periods ended December 31, 1997 and 1998 would have been increased by $11,000
and $60,000 and $0.01 and $0.02 per share, respectively. For purposes of
determining this compensation expense, the fair value of each option grant is
estimated on the grant date using the Black Scholes option pricing model with
the following weighted average assumptions used for grants during the periods
ended December 31, 1997 and 1998, respectively: no dividend yield, risk free
interest rates of 5.3 percent and 4.9 percent, respectively, expected volatility
of nil, and expected term of four years for common options and six months for
the preferred option.
 
NOTE 8--INCOME TAXES
 
    As of December 31, 1998, the Company had net operating loss carryforwards of
approximately $37,000,000, which are available to offset future taxable income
through 2018 for federal taxes and 2005 for state taxes, subject to the
limitations of Internal Revenue Code Section 382 relating to changes in
ownership of the Company. The deferred tax asset arising from the loss
carryforwards has been fully offset by a valuation allowance since it is more
likely than not that it will not be realized. The valuation allowance increased
by $13,905,000 during 1998, primarily as a result of the additional losses in
1998.
 
    Components of deferred income taxes are as follows:
 
<TABLE>
<CAPTION>
                                                         DECEMBER 31, 1997  DECEMBER 31, 1998
                                                         -----------------  -----------------
<S>                                                      <C>                <C>
Deferred tax assets:
  Net operating loss carryforwards.....................     $   908,000      $    14,724,000
  Accrued vacation and other...........................          89,000              178,000
                                                               --------     -----------------
Gross deferred tax asset...............................         997,000           14,902,000
Valuation allowance....................................        (997,000)         (14,902,000)
                                                               --------     -----------------
Net deferred income taxes..............................     $   --           $     --
                                                               --------     -----------------
                                                               --------     -----------------
</TABLE>
 
    The provision for (benefit from) income taxes reconciles to the statutory
federal tax rate as follows:
 
<TABLE>
<CAPTION>
                                                          DECEMBER 31, 1997    DECEMBER 31, 1998
                                                         -------------------  -------------------
<S>                                                      <C>                  <C>
Statutory federal tax rate.............................           (34.0)%              (34.0)%
State income tax, net of federal benefit...............            (5.4)                (5.4)
Other..................................................            (1.8)                 0.9
Deferred tax asset valuation allowance.................            41.2                 38.5
                                                                  -----                -----
                                                                 --    %              --    %
                                                                  -----                -----
                                                                  -----                -----
</TABLE>
 
NOTE 9--RELATED PARTY TRANSACTIONS
 
    The Company's in-house counsel is also a partner in a law firm used
externally by the Company. During 1997 and 1998, the Company incurred legal fees
and expenses of approximately $92,000 and
 
                                      F-13
<PAGE>
                          RHYTHMS NETCONNECTIONS INC.
 
             NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (CONTINUED)
 
NOTE 9--RELATED PARTY TRANSACTIONS (CONTINUED)
$1,269,000, respectively, to the external firm, in addition to the salary paid
to the in-house counsel. At December 31, 1998, the Company had a balance payable
of $372,000 to this entity.
 
    Two members of the Company's Board of Directors serve as directors to a
company that supplies equipment to the Company. The total purchases during 1997
and 1998 from the equipment supplier were approximately $419,000 and
$13,005,000, respectively. At December 31, 1998, the Company had a balance
payable of $2,451,000 to this entity.
 
NOTE 10--COMMITMENTS
 
    The Company leases office space and certain office equipment under
non-cancelable operating lease agreements. The leases range in term from 24
months to 60 months and, in certain instances, provide for options to extend.
Rent expense under the operating leases for 1997 and 1998 totaled $46,000 and
$2,044,000, respectively. Future minimum rental payments under the leases are
$11,169,000 in 1999, $11,251,000 in 2000, $9,667,000 in 2001, $1,710,000 in
2002, and $1,190,000 in 2003.
 
NOTE 11--SUBSEQUENT EVENTS
 
    Effective March 2, 1999, the Company amended its Certificate of
Incorporation to increase the number of authorized common shares to 84,527,584,
as adjusted for the November 1998 and March 1999 stock splits, and to authorize
3,731,410 shares of Series C preferred stock.
 
    Effective March 4, 1999, the Company issued 3,731,410 shares of its Series C
preferred stock to
MCI WorldCom's investment fund at a price of $8.04 per share for total proceeds
to the Company of $30,000,000. In connection with this investment, MCI WorldCom
also received warrants to purchase up to 720,000 shares of common stock at a
price of $6.70 per share. The terms of the transaction also provide for the
Company and MCI WorldCom to enter into various business relationships, including
MCI WorldCom's commitment to sell 100,000 of the Company's DSL lines over a
period of five years, subject to penalties for failure to reach target
commitments.
 
    During January and February 1999, the Company granted options to purchase
1,615,686 shares of common stock pursuant to the Plan. The grant of these
options will result in additional deferred compensation in 1999 and compensation
expense in 1999 and future years as the options vest.
 
    On March 19, 1999, the Company completed a six for five split of its common
stock. The accompanying consolidated financial statements have been restated for
all periods presented to reflect the stock split.
 
NOTE 12--SUBSEQUENT EVENTS (UNAUDITED)
 
    Effective March 15, 1999, the Company amended its Certificate of
Incorporation to increase the number of authorized common shares to 74,171,062,
as adjusted for the March 1999 stock split, and to authorize an additional
3,731,409 shares of Series C preferred stock.
 
    On March 16, 1999, the Company issued 3,731,409 shares of its Series C
preferred stock to Microsoft at a price of $8.04 per share for total proceeds to
the Company of $30,000,000. In connection with this investment, Microsoft also
received warrants to purchase up to 720,000 shares of common stock at a price of
$6.70 per share. The terms of the transaction also provide for the Company and
Microsoft to enter into various business relationships.
 
                                      F-14
<PAGE>
                          RHYTHMS NETCONNECTIONS INC.
 
             NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (CONTINUED)
 
NOTE 12--SUBSEQUENT EVENTS (UNAUDITED) (CONTINUED)
    The Company has filed a registration statement for a public offering of
approximately 9,375,000 shares of common stock.
 
    On March 16, 1999, the Company's Board of Directors approved the 1999 Stock
Incentive Plan and the 1999 Employee Stock Purchase Plan, subject to stockholder
approval. The 1999 Stock Incentive Plan is intended to serve as the successor
equity incentive program to the 1997 Stock Option/Stock Issuance Plan. An
initial reserve of 8,161,944 shares of common stock has been authorized for
issuance under the 1999 Stock Incentive Plan. The Company has also initially
reserved an additional 1,200,000 shares of common stock for the 1999 Employee
Stock Purchase Plan. The 1999 Stock Incentive Plan will become effective upon
the effectiveness of the public offering. The 1999 Stock Incentive Plan will
become effective upon the execution of an Underwriting Agreement for the public
offering.
 
    On March 31, 1999, the Company entered into a 36-month lease line that
provides for $24,000,000 in equipment on an operating lease basis. In connection
with this lease agreement, the Company issued 45,498 warrants to purchase common
stock at a price of $10.55 per share, exercisable immediately.
 
    Effective April 5, 1999, the Company restated its Certificate of
Incorporation to increase the number of authorized common shares to 81,000,000,
to authorize an additional 932,836 shares of Series C preferred stock, to
authorize 441,176 shares of Series D preferred stock, and to designate 1,000,000
shares as Series 1 junior participating preferred stock.
 
    On April 6, 1999, the Company issued 932,836 shares of its Series C
preferred stock at a price of $8.04 per share and 441,176 shares of its Series D
preferred stock at a price of $17.00 per share to a wholly owned subsidiary of
Qwest Communications Corporation for total proceeds of $15,000,000. In
connection with this investment, Qwest also received warrants to purchase
180,000 shares of common stock at a price of $6.70 per share and MCI WorldCom
received an additional warrant to purchase 136,996 shares of common stock at a
price per share equal to the initial offering price per share of the Company's
public offering of common stock.
 
    During April 1999, the Company entered into a 36-month lease line that
provides for $20,000,000 in equipment on an operating lease basis. In connection
with this lease agreement, the Company issued 75,000 warrants to purchase common
stock at a price of $10.55 per share, exercisable immediately.
 
                                      F-15
<PAGE>
       [MAPS OF SAN DIEGO, CA AND CHICAGO, IL SHOWING RHYTHMS DEPLOYMENT]
<PAGE>
- --------------------------------------------------------------------------------
- --------------------------------------------------------------------------------
 
                                9,375,000 SHARES
 
                                     [LOGO]
 
                          RHYTHMS NETCONNECTIONS INC.
 
                                  COMMON STOCK
 
                               ------------------
 
                              P R O S P E C T U S
 
                               ------------------
 
                              MERRILL LYNCH & CO.
                              SALOMON SMITH BARNEY
                               HAMBRECHT & QUIST
                           THOMAS WEISEL PARTNERS LLC
 
                                 APRIL 6, 1999
 
- --------------------------------------------------------------------------------
- --------------------------------------------------------------------------------


© 2022 IncJournal is not affiliated with or endorsed by the U.S. Securities and Exchange Commission