Do establishments have a real issue with Yelp?

In a comment to this post (http://icanhaz.com/yelp), Assaf says that some store owners think they're not getting a fair shake with Yelp. Like they are the victims of trolling, and they'd have to pay money to get it 'fixed' on Yelp. Any merit to this? Seems like it would be very damaging to Yelp if so. Ruin the credibility, so why would they allow such?