Feedburner has been running ads in feeds for a little while now. They have a slick self-service system for publishers to select which ads run in their feeds, which personally I've been happy with (it allows me to delete any 'offers' of ads with a $1 CPM gross - there are surprisingly a lot of advertisers who try to get away with that pathetic figure! Try $7 CPM, that's more likely to get the tick of approval). Now Feedburner has added the ability for publishers to put ads on their websites. CEO Dick Costolo is positioning this as another part of their 'feeds as a first class citizen of content' strategy. He doesn't use that particular phrasing (I think that's my pompous terminology!), but the title of his post says it all: The Feed Powers The Site.
"By using the content and the structure of RSS and Web feeds, FeedBurner gives advertisers unique new placements — such as continuous ads, ads that dynamically appear only on content posted within specific timeframes, ads associated with highly active content (e.g. blog posts with comments or those that have been emailed) and more."
Feedburner is banking on this extra feed-derived context to give them an edge over page-derived contextual ad networks, like Google Adsense and Yahoo Publisher Network. It's difficult to predict how successful this will be without testing it first via my own feed. Feedburner seems to be suggesting its 'ownership' and inside knowledge of a site's feed gives them extra contextual powers, which the likes of Google and Yahoo don't have just by analysing the text of each page/post. I'll test it out and let you know.