Yelp's filter is not much more than a traffic cop. It attempts to control traffic by driving it from listed non advertisers to paid advertising customers. Otherwise, why would the same reviews constantly go up and come down with the "switch" being spikes in views or actions on the non-advertising listed businesses? Nope. Yelp itself is about 40 to 50% scam.
Yelp's filter can not determine if a person walks by a restaurant or a hair or waxing studio and does a check-in to a business with which that fake customer has not really had a legit interaction, can it? No, it can't. Like I said, easy to game.
In addition, There has been a large upswing in so-called SEO companies which do nothing more than attempt to raise the Yelp ratings of their clients and at the same time post false negative reviews on their client's competition. Yelp is not able to stop that.
I have done a significant amount of research into Yelp's procedures and the way the site really works. Yelp's claims about it's filter are mostly nonsense.