Just like you know: http://www.digitalpoint.com/~shawn/2004/08/pageant-of-masters.html type is in fact banned by google. I designed somthing to let the ad to follow around the pointer. I was told any type of "redefiining" the behavior of adsense is banned. But in realilty, google does not check too much as long as you don't do the following: encourage for clicks automatic clicks
I once had a Google ad as part of a layer on my forums that would encourage visitors to join the forums. Google got on my case about it so I had to remove it.