Adsense for feeds Blog finally said Good Bye on 26th July 2012. Their previous post dated 25 October 2010.
Sometimes I wonder how much did Feedburner actually improved after Google acquired it !
Anyways once Adsense is added to your Feedburner it does not provide the level of control as provided in the website content.
The last post can be found at http://adsenseforfeeds.blogspot.in/2012/07/saying-goodbye-to-adsense-for-feeds-blog.html