WHAT DID AL FRANKEN KNOW, and when did he know it? When Air America launched last year, it was the beneficiary of more free publicity than any radio show or network launch had ever received. So desperate was the mainstream media to find some left-leaning response to the Limbaugh-led revolution in talk radio that the many and obvious flaws in the network's offerings went largely unreported. Those of us who have been around radio studios for a few years know, though, that launch hype and selective reading of Arbitron results can never mask the key question: Is a show profitable?...