They set a post-IPO low of $18.23 in early Friday trading, before recovering to $18.35, down $3.87, bringing the loss on investors who paid $19 in the IPO to nearly 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.
Since the insider sales began, Facebook shares have traded no higher than $19.73.
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