Facebook ( FB ) made a major well-publicized announcement yesterday. The company unveiled a social search tool that will leverage the data on its one billion members. This effort is seen by analysts as a shot across the bow of Google ( GOOG ), LinkedIn (LNKD) and Yelp ( NYSE: YELP ). My take is Google has little to worry about at this point as it is hard to s ee how this effort will impact its huge market share of web search and near monopoly on mobile search. Likewise, LinkedIn's models should be safe as most people want to keep their business and personal lives separate. However, this is a major blow to Yelp, a company I have been negative on and a stock I have been short since it was trading at $27 a share. Consider how Facebook's new search tool could upend Yelp's business model or at least take significant market share. Yelp's Model: Get reviews on restaurants, movies, shops etc… by what strangers are saying.