I just set up adbrite on one of my sites and deleted all my google ads. When setting up the ad zone, they asked if i use another ad network, so i chose yes, and then they asked me to enter my adsense code snippet so that they could rotate between their ads and adsense depending on which one has greater ecpm. I checked my site immediately after placing their code and ofcourse my google ads were gone since i had deleted them, and in place there was just one line "Your Ad here" in my ad zones. I checked again about one hour later and one of my google adsense skycrapers is back! I guess this is adbrite rotating the ads? Anyone experienced this before? Is it okay?
But does it violate adsense TOS? In some cases both adbrite and adsense may show at the same time on different ad spots.