Social reviewer Yelp (NYSE:YELP) is up huge so far this year, recently topping the $50 per share threshold. Much of the investor optimism is due to mobile revenue growth, but the company still faces threats from larger rivals like Google (NASDAQ:GOOGL), who tried to acquire Yelp years ago. As Yelp transitions to mobile, it will rely less on Google for traffic, which is a good thing.

In the following video, Fool contributor Evan Niu, CFA, and Eric Bleeker, CFA, discuss why Yelp has had such a good year, and whether or not the current valuation makes sense.