According to a recent article in The New York Times, the number of radio stations broadcasting on the Web increases by more 100 every month.  As of December 1999, that number had reached nearly 3,000.  Computer users with a sound card, speakers, and free software such as RealPlayer or Windows MediaPlayer can listen to radio stations anywhere in the world live from wherever they happen to be.  

The technology that allows this is called "streaming audio" and it involves compressing sound into packets of bits, sending the packets through the Internet, and reassembling them into a continuous stream.  It allows the computer at the receiving end to listen to the sound file as it downloads, rather than waiting for it to finish downloading before beginning to play.  This technology has improved considerably in the five years since its invention, although for users with low bandwidth connections, broadcasts can still be frustrating, warbling like they are coming from under water, stopping and starting erratically, or not coming in at all at times.

In the preface to the new edition of Technology and the Future I wrote of listening to a radio station in Accra, Ghana, on my computer while working on the book.  From the standpoint of the listener, webcasting widens the range of listening options far beyond the number of stations that can be received over the air.  For the broadcaster, the Web offers relatively low cost, freedom from government regulation (in the U.S., FCC rules do not apply), and the possibility of reaching nationwide or even worldwide niche markets.  All of this is going to change the face of radio in fundamental ways, especially if new appliances for receiving webcasts are developed that look and operate more like traditional radios than computers.  According the Times article, such devices are about two years away from the market.