OK, this is mostly just for fun, but fun with a point.
Broadcasting has forever been a one-to-many medium -- one transmitter, many listeners. With production and publication tools increasingly within the reach of nearly every web user, the web is now considered to be a many-to-many medium.
As an internal exercise last fall, I wanted to describe the many-to-many concept in a way that would be easy for broadcasters to internalize, so I sketched out a concept for a "many-to-many" radio. The result, which I've shown to a few people outside my station, was the drawing below (click to enlarge or access here).
What it depicts is a mash-up between an HD Radio and an Internet "radio." Interestingly, the HD Radio standard makes use of an open mark-up standard called Synchronized Multimedia Integration Language (more SMIL info at Wikipedia), a relative of the HTML standard that's used to build web pages. What that means is that it would be fairly trivial to program an HD Radio to tune many more channels than the three or four that come in via the broadcast spectrum such as standard Internet addresses accessible with a second built-in radio for WiMAX or some other 3G or 4G wireless service (most cell phones today contain multiple radios in one device). A station could transmit authorized Internet addresses (URLs) using the HD Radio's data capabilities.
The result would be a consumer device that, for each station in a market, could tune in dozens or even hundreds of program channels. Some of those might be in the clear, others accessible through conditional access. Of course it would take a willing consumer electronics manufacturer to build this thing, but just about anyone with HTML skills could "breadboard" the Internet part of it.
But how would one program it? That's where the many-to-many part comes in. Not to mention a possible army of copyright lawyers. One possible way to enable listeners to program their own channels would be to use RSS feeds from (in our case, public broadcasting) audio sources. A listener-programmer could go to your web site, sign up for a "channel" (URL), select from a list of podcast feeds like NPR's or PBS's, and arrange them to suit the programmer. When a listener tunes to a channel, the stream is triggered (unless someone else has already triggered it). When no one is listening, it goes away. When someone is listening again, the stream picks up where it left off. Old episodes are replaced by new ones via the RSS mechanism.
This has the potential of burning through a lot of bandwidth, so through subscription or contribution or pay-per-access or underwriting/advertising, one would have to recover those expenses. I'm sure there would be a number of other problems to work through, but as I said at the top, this is just for fun, right? --Dennis