An article in today's In These Times, titled "Bike-sharing is Caring" by Adam Doster, discusses the popularity of bike-sharing abroad and now in the U.S.
"Bike-sharing fever has even spread to the United States, a country lacking a robust bike culture but one where car-sharing has thrived and biking is becoming more mainstream. In San Francisco, the city Board of Supervisors is set to vote on a contract with Clear Channel Outdoor Inc. that would establish a bike-sharing program in return for advertising rights on transit shelters. Chicago Mayor Richard Daley visited Paris in September to test the Vélib in action and is considering a similar program for the Windy City. New York City, Portland and Washington, D.C. officials have also expressed interest."
In fact, D.C.'s "SmartBike" program is expected to launch in April/May 2008. Hang in there for updates.
Car-sharing has indeed expanded rapidly across the U.S. in just a few years. The recently merged Zipcar and Flexcar started up in 1999-2000 and now serve over 40 locations. I believe that bike-sharing could maintain this same pace.