It is among the biggest single-day falls in U.S. stock market history.
CNBC reported Facebook's performance Thursday "was on track" to be the "largest one-day loss in market value by any company", with its valued down $120 billion or more during the middle of the day, leaving a capitalization of $508 billion.
The single biggest loser is Mark Zuckerberg, Facebook's founder and chief executive, who owns almost 17% of the company.
His fortune tumbled in late trading Wednesday, as shares of the social media giant slid 20 per cent in post-market trading in NY on disappointing results.
Facebook's daily active users for the second quarter of 2018 were effectively flat in the US sequentially, and even declined in Europe compared with Q1 - marking the first time the company has seen such a decline in recent quarters.
Many had come to consider Facebook nearly immune to image problems, especially after the most recent scandal involving the British company Cambridge Analytica.
Still, the loss of users should not have shocked investors because Facebook has said for the past two quarters that it was starting to hit the zenith of user growth in its most mature markets like North America.
The introduction of a new European privacy law has knocked user growth and engagement.
"We're investing so much in security that it will start to impact our profitability, we're starting to see that this quarter", Zuckerberg told a conference call on quarterly results.
On a call with analysts, Facebook advised it expected its revenue growth rates to be lower than the year prior, especially in the second half of this year. Technology companies account for six of the 10 biggest companies in the S&P 500 Index. It reported 2.23 billion monthly active users and 1.47 billion daily active users, which were both up 11 percent year-over-year but narrowly missed estimates.
And things are about to get worse. Today, Facebook's chief legal officer announced he's departing at the end of this year for family reasons.
Advertising revenue for the quarter was $13.04 billion, missing analyst forecasts of $13.16 billion. Wednesday may have been the first time this tension really broke into the open, probably because it threatened the one thing all investors care about: Money.
Facebook has faced intense scrutiny over privacy issues and the spread of disinformation or "fake news".
Still, that was slightly below Wall Street expectations.
But Facebook is trying to find success with the three apps by emphasising Stories, a video and photo sharing format borrowed from Snapchat.
"Mark Zuckerberg isn't panicking", he said.
After these events, several senior leaders have departed Facebook, including a board director, its chief information security officer, and its vice president of communications, marketing and public policy.