> So it's a tough situation for Google, especially when you factor into account potential impact on all the advertising revenue they're generating from these spam sites.
Adsense revenue does not enter in to ranking decisions. Our evaluation process is far from perfect, but revenue is not part of it. We're not blind to the fact that a lot of scummy sites run adsense, but the even scummier ones have already been kicked out of adsense and now use other ad networks or affiliate programs. "Denying spammers revenue" has been at times the explicit goal of projects that launched.