Dr. Johnson asked Yelp to remove the review. However, nothing he tried—not even purchasing advertising from Yelp—would convince them to remove the review… Over the next three months, Yelp hid every review that patients left for Dr. Johnson. The only review that remained was the original bad review. And below the bad review was a line of gray text showing how many other reviews had been hidden.
Online user reviews have become incredibly powerful. A few weeks ago half a dozen dentists in my San Francisco audience had horror stories about how Yelp mistreated them. I hear stories of small businesses and restaurants being threatened by customers demanding a free meal or else they will write a bad online review.
I have personally never had a bad encounter with Yelp and Yelp vehemently denies they are doing anything wrong or filtering reviews based on pay offs.
The linked article by Dave Engel has six tips on dealing with Yelp. They all sound good to me especialy these; do not buy Yelp ads expecting to get rid of bad reviews but do claim your free Yelp profile.