Facebook's stock sank to a record low Thursday as some of the social networking company’s investors got their first shot since the initial public offering to sell shares. 
 
 Shares traded as low as $19.69 before coming to rest at $19.87, down $1.33 or more than 6%. More than 156 million shares traded hands, more than five times the average volume. 
 
 The spike in trading amplified fears that insiders were fleeing a company that, before its IPO in May, was one of Silicon Valley’s brightest. Shares of the IPO were priced at $38; since then the stock has lost nearly half its value amid concerns over slowing revenue growth and its future moneymaking potential, particularly on mobile devices. 
 
 It will be days before insiders have to disclose if they sold stock. But investors with a combined 271 million shares could have dumped their holdings Thursday when the first in a series of lock-ups expired. Among those who became eligible to sell shares: investment bank Goldman Sachs and venture capital firms Accel Partners and Greylock Partners. 
 
 “Certainly some of them sold. The question is how many of them sold and how much of their holdings they sold,” Pivotal Research analyst Brian Wieser said. 
 
 But, he said, “The big issue is, was and always will be November.” That’s when about 1.2 billion shares from insiders will be eligible to be sold. 
 
 Kevin Landis, chief investment officer at Firsthand Capital Management in San Jose, bought Facebook shares late last year on the private market. He paid $31.50 apiece. 
 
 “Lockup expirations have a lot to do with how Facebook will trade in the next couple of days and almost nothing to do with what the company will be worth a year or two from now,” Landis said. 
 
 The lockup on Firsthand’s shares expires in November. Landis says he doesn’t yet know if he will sell. 
 
 “Whatever happens this week is a dress rehearsal for November. That question is not going to be put to us this week. But in November that question will be put to us pretty hard,” Landis said. 
 
 It has been a dramatic reversal of fortune for Facebook, which went from having one of history’s most hotly anticipated IPOs to one of the most botched. Its market value has plummeted by almost $50 billion. 
 
 “I think Facebook has a lot of things going for it. Unfortunately the stock price has not been one of them,” S&P Capital IQ analyst Scott Kessler said. 
 
 All told, more than 1.7 billion new shares will be released onto the market over the next nine months, said Sam Hamadeh, CEO of PrivCo, which researches privately held companies. He says the share value of the lockup expirations at about $20 a share is nearly $35 billion worth, roughly equivalent to the entire market value of companies such as Starbucks and Target. 
 
 “There simply is no relief on the horizon for Facebook stockholders,” Hamadeh said. “It will get worse before it gets better.” 
 
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 How low will Facebook shares go? 'Lock-up' expires, stock plunges 

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 The fortune of Mark Zuckerberg, Facebook Inc. (FB)’s co-founder and CEO, dropped to a new low today. 
 
 Related Story: Facebook Falls to Record Low As Lockup End Frees Shares 
 
 The 28-year-old’s net worth fell to $10.2 billion, its lowest point since the company’s May 17th initial public offering, according to the Bloomberg Billionaires Index. Facebook shares sank 6.3 percent today after the company freed up 271.1 million shares, a move that boosted the amount of stock available to trade by 60 percent. The shares closed at $19.87 in New York after dipping to a record low of $19.69 earlier in the day. 
 
 “The market is not convinced of Facebook’s future,” David Kirkpatrick, author of “The Facebook Effect,” a history of the company, said in a telephone interview, adding that Zuckerberg probably isn’t worried about the sagging value of his own shares. “He thinks of it only in terms of how it affects the company’s strategic and tactical opportunities.” 
 
 While Zuckerberg’s fortune swooned, the 40 richest people in the world added $1.9 billion to their collective net worth, as the Standard & Poor’s 500 Index closed at its highest point since April. 
 
 Facebook is down 48 percent from its $38 offering price. The world’s largest social-networking company raised $16 billion in its IPO, the largest ever for a technology firm. With a market capitalization of $48 billion, Facebook has lost more than $40 billion in value since the offering, making it the worst performer among all large IPOs on record, according to data compiled by Bloomberg. 
 
 Founders Falter 
 
 The fortunes of Facebook’s other founders also took a hit. Co-founder Christopher Hughes, 28, owns about 22 million shares of Facebook, according to a person familiar with his holdings who asked not to be named because the matter is private. His stake is worth $437 million, down almost $400 million since the IPO. 
 
 Dustin Moskovitz, 28, who started the company with Zuckerberg, Hughes and Eduardo Saverin from a dorm room at Harvard University, owns 133.7 million shares of the company’s Class B stock worth $2.7 billion, a decline of $2.4 billion. 
 
 Saverin, 30, has a $1.1 billion stake, down $960 million since the offering. According to a regulatory filing dated May 17, he owns 53.1 million shares of the company. 
 
 Facebook Inc. director Peter Thiel, who sold more than 16 million shares in the company’s initial public offering, converted more than 9 million shares to Class A from Class B, according to a document filed Aug. 10 with the U.S. Securities and Exchange Commission. 
 
 Thiel, a venture capitalist and hedge-fund manager whose proceeds from the IPO topped $630 million, still holds a stake worth about $550 million. 
 
 Ashley Zandy, a spokeswoman for Facebook, declined to comment. 
 
 To contact the reporter on this story: David De Jong in New York at ddejong3@bloomberg.net 
 
 To contact the editor responsible for this story: Matthew G. Miller at mmiller144@bloomberg.net
– More stock woes for Facebook: As some shareholders got their first opportunity to sell yesterday, shares plummeted to a new low of $19.69. By day's end, they'd settled at $19.87, a 6% plunge, the Los Angeles Times reports. It's not clear yet how many of the 271.1 million shares that became unlocked yesterday were sold, but analysts have their eyes on November, when the lock-up period expires on 1.2 billion shares. Until now, Mark Zuckerberg had told staff to ignore the stock prices, but at a recent meeting, he noted that watching investors flee could be "painful," the Wall Street Journal notes, saying Zuck is working to brighten the mood at the office. He may need his own mood brightened: Bloomberg reports that Zuckerberg's fortune is at a new low since Facebook's IPO, the 28-year-old having lost $600 million yesterday. His net worth is now $10.2 billion.