«Public radio is riding high. Its audience has more than doubled in the last decade. About 27 million people now listen to public radio at least once a week, according to the Radio Research Consortium, a nonprofit organization that tracks audience data for noncommercial radio. That's a lot of people. Consider that Friends, the iconic TV series, has been pulling in around 20 million viewers in recent weeks.»
--"Radio Rich: While public television is on the skids, public radio is riding high. What's the secret? "
Maybe it's just easier to make good idea-rich radio than to make good idea-rich TV? Certainly the mere technical side is a whole lot easier to pull off for radio than for TV.