First, they have to control the distribution. Then, they have to build the tech, which will obviously involve some kind of DRM.
To say that I hope they fail is an understatement.
But I know they'll try because in the internet economy, companies simply must fight, kick, and scratch for every last fraction of penny of advertising revenue.
I hope that they are unable to wrest sufficient control over the distribution channels to force this ugly future upon us. Indie podcasts will be safe, but the well-produced, mainstream podcasts will go the way of cable TV and it will be gross. Ads ruin everything.