I am seeing more and more RSS feeds with advertisements in them. Most of the time the ad has been a separate rss <item>. As annoying as that can be, at least I can just nuke that one item (I use my email client as my news reader… so each item is basically like a separate email).
The Infoworld feed however, puts ads in the RSS content itself. This confuses many RSS readers as they think that since the content has changed, the feed has been UPDATED, and hence you end up with a ton of duplicates! What a pain.
I know a lot of sites are trying to work out how best to use RSS, as it is a very different model than we are used too… but come on!