I solve this by taking all reviews with a grain of salt. As I get to know a reviewer in whatever field, I'll give the opinions more weight - or less. I don't know Yelp myself, but I look at not just dozens but hundreds of food blogs, learning what I can, as a kind of hobby. I would trust David Lebovitz, for example, about pastry shops in Paris, should I ever be lucky enough to go there. I'd listen to a2k's Francis about his favorite restaurants there - before I'd listen to a smattering of people I don't know on Yelp or Chowhound or another site I forget the name of, something like "city data".
On the other hand, if I see a lot of consistent complaints about a hotel on one of the travel websites I follow (again, a near hobby), I would take those into account.