Shares of Facebook (Nasdaq: FB), the No. 1 social networking site, went into a freefall Tuesday, plunging about 2.5 percent to keep setting new lows. After falling as low as $17.58 in late morning, they recovered slightly to $17.63, down 43 cents, after the first two hours of trading.

The Menlo Park, Calif., website raised $16 billion in its initial public offering on May 17, setting its IPO price at $18. Shareholders at the IPO price have now surrendered about 54 percent of their value.

At least no Facebook insiders have reported sales as they did after the lockup period expired two weeks ago, Since then early investor Peter Thiel sold 20 million shares and co-founder Dustin Moskovitz sold 950,000 shares. More than a billion shares awarded to employees at prices exceeding the market price will become marketable in the next 60 days.

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