Yelp has a history of salesmen selling business the right to mess with their reviews [1] [2]. I don't love Google, but I'm confident they will end that. (Yelp claims to have ended it already, but they have already lost my trust)

[1] http://www.jwz.org/blog/2009/02/yelp-shakedown/

[2] http://articles.latimes.com/2009/feb/11/business/fi-lazarus1...