Google has formally announced Adsense for Feeds, a program that displays both contextual and placement targeted ads in FeedBurner feeds. Feedburner's advertising network (FAN) has officially been closed and no new applications are being accepted.

AdSense for Feeds lets affiliates create a new ad unit that is automatically sized for a specific feed (either 468x60 or 300x250). "Generally, the 300x250 size will display when there's more content and when your feed is being viewed in a device with a larger display," explains Google. Affiliates can choose if they want image ads, text ads or a combination, the ad frequency (every feed item, every 2nd, 3rd, or 4th item), the position (top or bottom of the post), the colors and a channel that tracks the ad performance.

There is no connection between AdSense accounts and Feedburner accounts, so Google adds the service to your AdSense account directly. The downside is that feeds need to be migrated manually. Google has temporarily paused processing new manual migration requests as of this morning. Bloggers are able to burn new feeds automatically within their Adsense accounts however.

RSS advertising has never had much in the way of mass adoption (perhaps because of low RSS adoption as a whole) but this may give it the push it actually needs to become a valuable advertising medium.