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SAN FRANCISCO -- Yelp's early backers apparently still have a high opinion of the online business review service, much to Wall Street's relief, after insiders at several other Internet companies dumped some of their shares at the first opportunity.

A Wednesday increase of more than 22 percent n Yelp's stock price signaled the company's major shareholders are holding on to their stakes instead of seizing on a chance to reap the gains that have accumulated from investments made before the 8-year-old service went public in early March.

The first selling window for Yelp's insiders opened Wednesday with the expiration of a rule requiring them to hold on to their stock for 180 days after the company completed its initial public offering.

The end of other post-IPO "lock-up" agreements hammered the stocks of Internet social networking leader Facebook and Yelp rival Angie's List earlier this month. Their stocks plunged because some of their early backers pared their holdings, raising questions about whether the insiders had lost faith in the companies' long-term prospects. The biggest concerns hovered around Facebook after its first outside investor, former Internet executive-turned-financier Peter Thiel, sold about 20 million shares to get rid of most of his stake in the company.

A similar insider exodus at online coupon service Groupon and Web game maker