Targeted Ads in RSS
Ars Technica has started embedding advertisements in their RSS feed. I've seen this done in bootleg feeds, where the feed maintainer includes advertisements from the original publisher's site, but the Ars method is a bit cleaner and not done by a third party. The ad is actually an image, not any fancy HTML.
They could work on their targeting, though:
![Advertisement for breast form double-sided tape, embedded in the Ars Technica RSS feed.]
Update: As of 10:00 PM EST, 27 January, I no longer see the ads in the Ars feed inside Bloglines.