Up until now they have been using Google’s supply of advertisers to fill ads on their sites but wish to cut Google out of the equation and get into the ad business themselves.
Word is emerging on this new direction as they approach affiliates from their associates program to find if they would like to be involved in a beta test.
This could be difficult for them to do as many (if not most) of their Affiliates would currently be running AdSense or YPN ads and need to remove these current ads in order to beta test Amazon’s offering (as AdSense and YPN no not allow contextual ads on the same site page).