Comment by pbz

What Yelp does is a racket, similar to what BBB does. In Yelp's case they are being helped by Google and other search engines. The problem is that when people link to them that's an upvote in Google's eyes. After enough upvotes are gained, provided they don't spam, there's little anybody can do to downvote them. It's not like you can negatively link to them. This, I feel, is one of the main problems with the like and +1 buttons. There's isn't a -1 or notlike option.