On the most recent podcast411 (pluggd episode link) Rob goes on a soapbox as he plays an edited Jay Thomas (of sirius radio) interview with Keith and the Girl. Rob, as usual, is very aggressive; but he also makes some very good points. Of particular note he does an interesting, all be it simple, breakdown of the numbers when it comes to comparative audience sizes of a popular podcast and a satellite radio show.
What set Rob off was Thomas' advice to podcasters: that once they get big enough they should try to get a satellite radio show so that they can become even bigger. What Rob points out, at least what I took from it, is that if you have a popular podcast you probably already have a larger audience than you could hope to get on satellite (notable exceptions like Howard Stern aside). Certainly there may be other factors that would make being on satellite more appealing than having a podcast show: for example a steady (or any) pay cheque. But as far as the medium goes, I don't think most Sirius personalities realize that they are in a real battle with podcasts. Sure, listening to podcasts instead of listening to the radio requires a paradigm shift in the mind of listeners. But so does paying for radio. In the end there may be room for both but, after listening to Rob, I don't think there is a clear winner at the moment.