Yelp actually ripped off the Yellow Pages. The name comes from YEL-low-P-ages. The Yellow Pages was a paper-based business telephone directory that started decades earlier.
Oh, for sure, but comparing the state of Yellowpages.com now to its state in 2014, it's clear that someone decided to make the design and UX uncannily similar to that of Yelp. Of course Yellow Pages the concept was around before Yelp.
However, YellowPages.com ripped off the concept of yellow pages just as much as Yelp.
I'm saying that the YellowPages.com is a ripoff of the Yelp design and experience. If you changed just the logo and the color, it would look identical to Yelp, or at least how it looked before the recent redesign. Of course business listings and ratings are nothing new.