Google's AdSense ads have started showing up in RSS feeds from a few different publishers. At present, they're just testing the concept, so not many publishers are able to participate, but it sounds like the program will be expanding soon. This will likely lead to more feeds carrying full content, rather than just summaries or headlines in order to bring traffic to the publisher's website. I expect that once I can put AdSense ads in my feeds, I'll offer full content feeds with ads and summary feeds without.

• Silicon Valley Watcher: Google is testing ad placements for RSS feeds
• Google ads on our RSS feeds - The Peer-to-Peer Weblog - p2p.weblogsinc.com _