Those banners are really affiliate links as the site gets a commission if you purchase something by using the links. The site receives no add revenue unless the links are used (and a purchase made).
It's not really new as there were Google adds there before, they (the affiliate links) were just not viewable by registered members. I moved the Google adds to the center of the forums and placed the affiliate links up and to the right (as that is the most unobtrusive and unused space I could find).
I'm also going to code a page that has all the affiliates listed as well as putting an option in your preferences section under you control panel to turn it off (in the near future).