e compa- ny's backbone routers were located. Other backbone ISPs did the same, of course. This then led to a number of start-ups of companies whose sole business was hosting other companies' servers. Perhaps the best known was Exodus Communications, founded in 1994, which grew to 48 data centers by the time it went bankrupt in 2001 [13]. Exodus did not, however, own its own backbone transmission facilities, which may have contributed to its inability to turn a profit. Internet Traffic Explodes as the Public Joins The amount of bandwidth on the Internet had been growing at a rapid pace for many years before the NSFnet backbone was privatized. The ARPAnet's The Great Telecom Meltdown backbone links, into the early 1980s, were largely made up of 50,000 bps cir- cuits. That was no small feat to achieve, because an analog voice-grade leased cir- cuit at the time could, in general, only support a 9,600 bps modem. The backbone was built using group channel modems, Bell type 303, each of which consumed the bandwidth of 12 voice channels on the AT&T Long Lines net- work. By the time of the NSFnet, 1.544 Mbps "T1" circuits were readily avail- able, and by the time of privatization, the busiest backbone routes were starting to migrate to the DS3 rate of 44.7 Mbps, roughly a thousand times faster than the old ARPAnet backbone. That was only the beginning. Internet backbone bandwidth requirements were growing rapidly for two reasons. One was the increased bandwidth used by the average subscriber, as new applications, lower-cost and higher-speed links, and faster computers facilitated more intensive use. The World Wide Web only began to catch on after the introduction of Mosaic in 1993, yet by 1996 it was wide- spread, making the Internet far more attractive to consumers. Electronic mail traffic grew as more people became reachable. And the opening of the net- work to the public created the scourge of spam, as unscrupulous marketers began to harvest e-mail addresses from any possible source, and sell them to each other. Far mo