Last week, social kingpin Facebook ( NAS: FB ) saw the fateful expiration of its lockup period, setting loose over 270 million shares, free to find new homes, as their owners dumped them en masse. Shares fell 6% that day to fresh lows, only to briefly dip even lower -- below $19 -- on Monday. Subsequent SEC Form 4 filings show that early investor Peter Thiel cashed out just over 20 million of his shares near an average of $20 per share, pocketing almost $400 million in the process. The sales took place between August 16 and 17 through various funds, limited partnerships, and LLCs that Thiel has a beneficial ownership interest in. Thiel was an early Facebook investor, buying a 10% stake for just $500,000 as early as 2004, when Facebook was valued under $5 million. He also sold 16.8 million shares through Facebook's IPO in May at the offering price of $38, bringing in $638 million.