You should ask Powerscore or Testmasters if they want a little ad. I know they don't really do that, but they'd get tons of business/clicks from this site with everyone raving about them. If someone read how awesome their prep books/courses/etc were, and then saw a little link/add, they'd be more inclined to click on it.
It will depend on how many people click it and then sign up for Kaplan. It's just an experiment right now - probably going to implement a sophisticated ad system to control that space. I hope it's not too annoying. Is it too annoying?