Jason takes an interesting look at RSS advertising. The coolest part of this blog entry is the interview with the creators of the some of the big RSS readers.
I actually think that RSS advertising holds some terrific potential. Because of the completely opt-in nature (no one thinks “Hey, I never added this RSS feed to my reader!” like people do with email subscriptions), I can see subscribing to a “Cool Commercials” or “Hot Deals” or “New products from Sony” RSS feeds.