Maybe this is sad news to all publishers who enabled ads on feeds as AdSense for feeds is going away. AdSense will stop serving feed ads on December 3, though I’m not using Adsense for now I think this is a sad news to all Adsense for feeds users.
Google Adsense for Feeds Ends by December
If you are using AFF you will not able to see ads on you on you’re My Ads tabs on December 3, 2012. And for those who are not using this product Adsense for feeds option will no longer available starting December 2, 2012 onwards.
As this change take effect it will not affect any other Adsense products that you are currently using. This will only take effect to those who uses Adsense services on feeds.
For more details and you may read http://support.google.com/adsense/bin/answer.py?hl=en&answer=2777193.