While Yelp boasts more reviews than Foursquare, at 42.5 million, the growth rate is lower than Foursquare's, at 41% year-over-year. But what's most remarkable is that Foursquare is outpacing Yelp in the review department, despite having a fraction of the public company's users. Yelp has roughly 108 million users, whereas Foursquare has just 35 million.