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

They set a post-IPO low of $18.23 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.