The registration statement indicates that there will be two classes of stock, Class A common stock, which is to be sold in the IPO, and Class B common stock, which has super-voting rights that will be held by insiders.
Link to the Company press release: http://www.prnewswire.com/news-releases/yelp-files-registration-statement-for-proposed-initial-public-offering-134058533.html
Link to the S-1 registration statement: http://www.sec.gov/Archives/edgar/data/1345016/000119312511315562/d245328ds1.htm
Link to Bloomberg story: http://www.bloomberg.com/news/2011-11-17/yelp-files-to-raise-100m-in-ipo.html
Link to Forbes story: http://www.forbes.com/sites/tomiogeron/2011/11/17/yelp-files-for-100-million-ipo/