As investors raced to buy shares, the sprawling social network raised $16 billion Thursday, in an initial public offering that valued Facebook at $104 billion. While the IPO shares, 421 million of them, are being sold at $38 each, the feverish anticipation of their debut could drive them higher Friday when the stock starts trading about 11 a.m. Newly public technology stocks - particularly ones that have captured investors\' attention like Facebook - often garner double-digit gains in a one-day pop. Investors who buy Facebook shares are taking a stake in a unique and potentially valuable business. But they are also exposing themselves to the risks posed by a relatively young company operating in uncharted territory. The IPO signals a rapid evolution for the company. In just eight years, Facebook has gone from a scrappy college service founded in a Harvard dormitory to the third-largest public offering in the history of the United States, behind General Motors and Visa. Investors now consider Facebook more stalwart than startup. At $104 billion, the social network\'s market value is higher than those of McDonald\'s, Citigroup, Amazon and all but a handful of other American companies. \"Facebook is here to stay,\" said Navin Chaddha, a managing director of the Mayfield Fund, a venture capital firm. \"It\'s a virtual economy where people are spending more time than any other Internet property.\" Facebook will be celebrating the occasion with the same style on which it built its reputation. The social network planned to celebrate its 31st \"hackathon\" on Thursday night, with engineers coding into the wee hours, employees amped up on Red Bull and staffers-turned-DJs playing their tunes, Facebook said. Part work, part fun, the Facebook tradition, which will take place in an area of the company\'s campus known as Hacker Square, encourages employees to do what they do best brainstorm, design and create. On Friday, Mark Zuckerberg, the hoodie-wearing founder whose stake after the IPO is worth $19 billion, is set to ring the opening bell for Nasdaq from Facebook\'s headquarters in Menlo Park, Calif., surrounded by executives, engineers and other employees. Shares of Facebook, which will trade under the ticker FB, will start selling to the public later in the morning. For now, Facebook seems to be a must-own stock. As the largest player in the social media arena, Facebook has been enjoying blue-chip status from the start, with investors worried about missing out on what could be the next Google. The social network will also soon join the Nasdaq 100, the technology index, so money managers looking to track the benchmark will join the swell of demand in the coming months. The frenzy for Facebook was on full display in the weeks leading up to its IPO. On May 4, JPMorgan Chase, one of the IPO bankers,redecorated its Manhattan headquarters with a giant Facebook flag and welcomed the company\'s management team to discuss the scheduled roadshow. Before an equity sales team of 300, Jamie Dimon, the firm\'s chief executive, made a rare appearance. Alongside him was the deal maker Jimmy Lee, who affectionately called Facebook \"the next great blue-chip.\" In the weeks that followed, investors packed hotel ballrooms to hear Facebook executives give their pitch. Bankers drew up waiting lists for the events, which included stops in New York, Boston and Palo Alto, Calif. The tour yielded an avalanche of orders. With investors lining up for shares, Facebook raised its price range and increased the size of its offering. Even so, demand from investors in the United States alone outstripped the number of shares by 30 times, according to one person with knowledge of the situation, who requested anonymity because the matter was private. On Thursday, the underwriters met one more time at Facebook\'s headquarters to settle on a final price. The bankers, along with Facebook\'s chief financial officer, David Ebersman, discussed a price as high as $40 a share, above the estimated range. While demand was strong even at that level, the largest institutional investors, the pillars of any offering, pushed back a bit on the valuation. By early afternoon, the stock price was set at $38.