Shares of Facebook (Nasdaq: FB), the No. 1 social networking site, set another new record low eight days after insiders were first allowed to sell out after the May 17 initial public offering.

They set a post-IPO low of $18.03 in Friday afternoon trading, after trading as high as $18.70. They closed at $18.08, down $1.01, their lowest-ever close. The loss to investors who paid $19 in the IPO now exceeds 52 percent.

After the lockup period on insiders expired, Peter Thiel, an early backer, as well as co-founder Dustin Moskovitz, sold more than 21 million shares of Facebook, of Menlo Park, Calif.

On Friday, EMarketer shaved $1 billion from Facebook's projected 2012 revenue, with a new projection of only $5.04 billion. Several analysts, such as Merrill Lynch's Justin Post, lowered target prices for the shares. Post trimmed his to $23 from $35.

Since the insider sales began, Facebook shares have traded no higher than $19.73.

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