Yes, they use bots to beat cheaters http://www.cs.cmu.edu/~biglou/ESP.pdf
That's different than using bots to interact with legitimate users.
Watch Luis von Ahn's presentation of the ESP game at http://video.google.com/videoplay?docid=-8246463980976635143&q=carnegie+mellon+image+game. It's very entertaining and you'll even learn why spammers host free porn sites even though they aren't in the porn business.