Google has made a habit of shutting down services it doesn’t find viable. This was the case with Google Wave, and now it’s AdSense for Feeds’ turn.
Google has sent an email to those using the service. I still had it on a website’s feed although, by the looks of the revenue, I can understand why the company is closing it.
The news is also on the Google support page. The note also says that if you’re using the service, you’ll still get earnings that will remain in your account until December 3rd. After that date, ads will no longer be served to feeds and that will be it.
Your Feedburner account won’t be affected so you don’t have to make any changes.