Facebook shares slumped around 5% as markets opened at the end of a 'lock up' of millions of the company's shares.
The fall comes as investors were given the opportunity to sell 'locked up' stock for the first time since the company's flotation.
Following the social media network's notorious initial public offering (IPO) in May, the lock-up period that forced pre-float investors to keep hold of shares will end, flooding the stock exchange with an extra 271 million shares.
When Facebook went public three months ago, 421 million shares were issued at $38 (£24.20) each, rising as high as $45 (£28.66) each after trading began.
But, since then, concerns have been raised over the company's falling share price, closing on Wednesday at $20.74 (£13.21) per share.
Analysts are now questioning the moves shareholders, including Goldman Sachs (NYSE: GS - news) and Microsoft (NasdaqGS: MSFT - news) , will make - testing their long-term investment commitments to the social networking site.
But Steve Place, a founder of options analytics firm investingwithoptions.com, said the drop in Facebook's share price could be a good thing for the company.
He said: "If Facebook was trading at $30 (£19.11), we would see a much larger effect from the lockup expiry. But at $20 (£12.74)? Not so much."
Mr Place explained that investors may choose to hold onto their stock in the hope its value will rebound and head back up.
Later in the year, yet more shares could hit the market, with 243 million available from October and a further 1.2 billion in November (Stuttgart: A0Z24E - news) .
Facebook's chief executive Mark Zuckerberg is obliged to keep hold of his stock until November 14.
It comes as reports have emerged that advertisers may soon be able target Facebook users more directly by posting adverts onto their news feeds.
Currently companies only have the ability to advertise products or brands to users who have 'liked' their pages.
Facebook is believed to be testing the scheme which, if successful, would open advertisers up to the site's one billion users, who have not necessarily become fans of particular brand pages.