companies that do not pay yelp for advertising he identifies cases where yelp has deliberately filtered out positive reviews authorized to sell ads, he feels. >> those suddenly vanished. >> they didn't say this but maybe they insinuated that maybe some of these bad reviews might disappear and some of these good reviews might stick. >> they'll help direct more traffic to your site and get you more positive reviews. >> implicit if you don't, we're not going to fix this and you're going to be stuck. and this happens time after time after time. you can go all across the country and hear the same story repeatedly. >> on your side story involving a local business and the website yelp. >> local business owner calls a review company's practices unfair. >> they report on controversy over the company's alleged sales techniques. >> in fact, the ftc has recorded well over 600 business complaints about yelp. many following this same pattern. and in california, a class