Facebook Inc. (FB), operator of the world’s most popular social-networking service, climbed to an all-time high today as investors bet the company will benefit from growing demand for its mobile-advertising products. Shares advanced 3.3 percent to $45.04 at the close in New York, a record that also surpassed the intraday high of $45 on the stock’s first public trading day in May 2012. Is Facebook overvalued? How do you think?