The following commentary comes from an independent investor or market observer as part of TheStreet's guest contributor program, which is separate from the company's news coverage.NEW YORK ( Trefis) -- Yelp ( YELP) is one of the largest online business search, review and recommendation service, which enables consumers to access ratings and read reviews and opinions about local businesses like hotels, restaurants, salons, dentists and mechanics on their website. Local businesses are reviewed and rated by contributors. Yelp generates revenue mainly from local business advertising, display advertising and from additional services like Yelp deals, and deals with reservation services like OpenTable ( OPEN). It competes primarily with other online business review services like Google ( GOOG) Places, Yahoo! ( YHOO) Local, Angie's List ( ANGI), CityLocal and Gumtree; display advertising players like Google, Yahoo!, Facebook and AOL ( AOL); and daily-deal sites like Groupon ( GRPN) and LivingSocial.