Shares of Facebook plummeted Tuesday even as the Nasdaq showed slight gains

Investors are continuing to hammer Facebook just 11 days after its initial public offering, sending the stock of the social networking powerhouse down 9.6 percent in trading Tuesday. The stock closed at $28.84, the first time it has finished below the $30 mark. Facebook went public at $38 per share earlier this month, with many questioning the lofty $104 billion valuation that was placed on the company at the time.

It is now valued at $61 billion.

Forbes reports that CEO Mark Zuckerberg saw his paper wealth decline by $1.5 billion Tuesday, valuing him at $14 billion. Meanwhile, Zynga, the social gaming company whose business is directly tied to Facebook, also has been hit hard in recent days. On Tuesday, it lost nearly eight percent of its value, part of a 12 percent slide over the past five days.

Instagram’s valuation also has dropped below the $1 billion mark to $963 million, following the proposed acquisition offer from Facebook which combined both cash and stock, according to PrivCo. Reuters also reports that Facebook’s purchase of Instagram will receive a lengthy review by the Federal Trade Commission.

Microsoft, which invested $240 million in Facebook in 2007 for a 1.8 percent stake, also has seen its investment plunge. However, the company sold 6.5 million shares as part of the IPO, recouping about $250 million.

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