Just not one big enough to sell ads for. Their ratings are lower than that for Norwegian hip-hop (stealing my own line from another thread).
There are many progressive shows on radio now that have no connection to Air America.
Most, if not all, of which pre-date Air America and have survived despite Air America making them look stupid by association.
This is OT but I just now watched a Harold Ford for Senate campaign commercial on Don Imus and it looked like Ford was making his political pitch from inside a church building. Has anybody else seen this Ford commercial and do you know if that was the interior of a church? If it was, it was in poor taste. Oh, and what happened to the Democrats yakking it up about keeping religion out of politics?