RSS feeds are great for those people who want to follow up on news sites without having to constantly revisit the same site multiple times a day. Google FeedBurner offers nice statistics to any sites with RSS feeds, allowing them to see how many subscribers they've got by hosting the RSS feed. What I'm finding increasingly annoying is the other service which FeedBurner offers - their advertising programme.
I don't mind if RSS feeds are either partial feeds to show users the first paragraph to attract users to visit the site, or full feeds to show users the entire article, however putting in adverts is highly annoying. To me RSS feeds are there to entice me to go and visit the site itself. RSS feeds are mostly used by fairly technical users - putting in adverts where the people reading them are most likely to ignore them seems a bit pointless. Adding other little buttons/icons to enhance the feed is annoying as well, I just want the article and nothing more!
I don't usually bother with advert blocking, but after seeing more feeds with adverts in I've finally installed Adblock Plus for Firefox. Good riddance to pointless adverts!