FeedBurner has recently closed FAN, its advertising network. "No new applications for FAN publishers are being accepted and we expect the broad variety of options provided through AdSense (including the new AdSense for Feeds product, powered with FeedBurner feeds) will give publishers valuable new revenue-earning potential," says a FeedBurner/Google employee.
The new AdSense for Feeds option lets you create a new ad unit that has a format automatically selected from 468x60 and 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. You can choose if you want image ads, the ad frequency, the position (top or bottom of the post), the colors and a channel that tracks the ad performance.
For the moment, there's no connection between your AdSense account and the FeedBurner account, so Google automatically adds the FeedBurner service to your AdSense account. Unfortunately, your feeds are still connected to the old FeedBurner account and you need to migrate them first. The migration process is manual: just send an email at adsense-support-aff@google.com and mention your FeedBurner username and the AdSense account email address.
From AdSense, you can easily burn a new feed by entering the address of your blog and selecting some tracking options. The feeds can be managed at the new FeedBurner site, but there's no visible change other than the integration with Google Accounts and the new URLs for feeds: http://feedproxy.google.com/NAME.
Here's an ad from a feed of a FeedBurner/Google employee:
I doubt that these ads are an effective way to monetize feeds, since people use feed readers to get timely updates from a lot of sites and spend less time for each item. Besides, feed readers are mostly used by tech-savvy readers that are less likely to click on ads.
At some point, I may experiment with some infrequent ads in Google Operating System's feed and I'll post my findings.
Resources:
AdSense for Feeds Help Center - you should read the tips
Migrating an existing FeedBurner account
The new FeedBurner homepage