Shares of Facebook (Nasdaq: FB), the No. 1 social networking site, fell to a new record low of $19.01 in midday Friday trading, a day after insiders were allowed to sell as many as 241 million shares they had been required to hold since the May 17 initial public offering. Volume of 67 million already exceeded the three-month daily average of 48 million shares.

The decline means shares of the Menlo Park, Calif., company have lost 50 percent of their value, a record for Internet companies, in only three months. Facebook raised a record $16 billion in its IPO, when the shares were priced at $19 by underwriters headed by Morgan Stanley (NYSE: MS), Goldman Sachs (NYSE: GS) and JPMorgan Chase (NYSE: JPM).

In early afternoon trading, Facebook shares recovered slightly to $19.19, down 68 cents, lowering the company's market value to only $41.2 billion.

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