Yelp ($YELP) uses an automated review filter to suppress some user reviews of businesses.  The review filter's criteria aren't publicly disclosed, and some businesses feel that legitimate positive reviews from happy customers are unfairly hidden.  One business owner, an operator of three restaurants in Mammoth Lakes, California and a Yelp advertiser, got so frustrated with the review filter that he challenged Yelp's review filter in court.  Recently, the court ruled decisively in favor of Yelp, confirming that Yelp isn't legally liable for filtering users' reviews as it sees fit.