Advertising in RSS feeds isn’t totally new, but it is becoming more common place. Whenever I see feeds with ads at the bottom I don’t mind TOO much, as I know that these companies are just trying to make some money, and I am good at ignoring them (unless they do a great job of giving out REAL content).
Dave saw, what I recently say, when TheServerSide added ads via pheedo. In this case it was just a (hopefully) one of mistake.
The biggest annoyance is when feeds are not setup correctly. I have had a few feeds, where a day later, and I have 10 duplicates of the same entry, with the only difference being the ad content at the bottom!
This is unacceptable, and has the affect of making people unsubscribe to the feed.
So, if we DO have to go with ads in feeds as more people use feed readers to get their content, lets at least be smart about it.