I'm still gearing up to jump into the podcasting game -- I think it's a very clever application, and a way of expanding to the general public what Audible's been doing with their subscription service for a while now.
The HUGE, 800 pound gorilla on the table is music licensing. As folks are using tools like GarageBand to make their podcasts sound like radio shows, the spectre of licensing hangs over all our heads. It was enough of a fiasco to get through the CARP proceedings, which pretty much hustled mom-and-pop stream providers out of existence (unless they use an umbrella service like Live365). Podcasting could raise these issues/problems all over again.
Podcasters may feel it's right/okay to put a song in a pdocast because of the promotional benefit to the artist, but not every artist feels that way. And the Library of Congress certainly feels that artists need to be compensated PER LISTEN.
If you're an artist that actively wants to have their work included in podcasts, you should be saying so right now on your websites and in your e-mail newsletters.
...and if there's enough interest, perhaps we'll put together a directory of musicians who are actively interested in releasing their music to podcasters? Tell me so in the comments and I can get behind the effort.