Yelp has successfully defended it’s self from several such lawsuits, on the other hand it’s also been sued several times over this. So, it’s a little past just internet rumors.

The simple fact Yelp lets companies pay to highlight a favorable review is IMO enough to destroy their credibility. Worse they directed customers through GrubHub for an unearned commission which is as far as I can tell simple fraud. But, that’s not what people are alleging here.