Lock-up over, Facebook stock slides

A magnifying glass is posed over a monitor displaying a Facebook page. (AP / Joerg Koch)

This week, Facebook employees became eligible to sell restricted stock for the first time. It follows the August expiration of a similar lock-up period covering Facebook's early investors and some directors. Others shares will become eligible for sale in the coming months.

Up to 1.5 billion more shares could flood the stock market -- about 3.5 times the 421 million shares that had been trading since Facebook's initial public offering in May. The 1.5 billion figure includes shares released from lock-up already.

On Aug. 16, a lock-up period expired for 271 million shares held by early investors and directors who had participated in the IPO, though CEO Mark Zuckerberg was excluded for unspecified reasons.

On Monday, the lock-up ended for 234 million shares and stock options held by employees as of Oct. 15, excluding Zuckerberg. Wednesday was the first trading day since then because of stock market closures resulting from Superstorm Sandy.

Here's the schedule for remaining lock-up expirations, as reported by Facebook Inc. in regulatory filings: