Maybe we've reached Peak Facebook.
Facebook shares nosedived Thursday morning, chopping more than $100 billion off the market value of the world's largest social network as investors wrestled with an earnings report that suggested the once unthinkable: slowing user growth.
The drop, which followed a free fall in Wednesday's after-hours session, is the largest-ever single-day collapse in terms of market capitalization, the value of all of a company's shares added together, in Wall Street history.
The plunge highlights concerns that Facebook users aren't flocking to the social network in the numbers they previously had. In the US and Canada, the company's core market, the monthly user figure stood flat at 241 million. In Europe, another important market, user figures fell. Growth in both daily and monthly average users, measures of how often members visit Facebook, missed analyst estimates.
The social network declined to comment on the market reaction to its earnings. On Wednesday, executives said investments in new products, like its much-touted Stories format, had weighed on revenue growth, and that growth will slip by "high single-digit" percentages over the next two quarters.
The stagnant user growth underscores anxiety that Facebook's myriad problems are prompting people to be more careful about using its huge and powerful platform. That would be understandable, given a massive data privacy scandal and an ongoing controversy over allowing fake news to remain in its news feed feature.
The company has also been vilified for failing to fight Russian trolls who exploited the social network to influence the 2016 presidential election. Just this week, Facebook was slammed for allowing Alex Jones, the InfoWars founder, to level an ugly, unsubstantiated allegation against Robert Mueller, the special counsel investigating Russian interference in the election.
Earlier this year, CEO Mark Zuckerberg was summoned to Capitol Hill to answer questions about the social network's behavior. The company has also invested in advertising transparency features as well as AI to identify fake news.
"We will continue to invest heavily in security and privacy," Zuckerberg said during an earnings call with investors Wednesday. "This is our responsibility to keep people safe."
The dovish sentiment hasn't mollified some. Thewrote on Wednesday an open letter to Zuckerberg detailing the harassment they faced from conspiracy theorists on the social network after the 2012 massacre. "We have endured online, telephone and in-person harassment, abuse and death threats," they wrote in the letter, which was published in The Guardian.
The stock drop may presage a broader investor backlash against Zuckerberg. In June, investor Trillium Asset Management proposed that Zuckerberg be removed as chairman of the social network. The investor blamed Zuck's "mishandling" of the data privacy scandal, which involved consultancy Cambridge Analytica grabbing gobs of personal details about 87 million users, and Russian involvement in the election.
"Adopting [our proposed] changes will have a long-term impact," said Jonas Kron, director of shareholder advocacy for Trillium Asset Management. The investor's concerns go back further than one quarterly report from the social network, he added.
This isn't the first time investors have called for changes at Facebook. In May, a coalition that included investors called on fund managers to pressure the company to implement stronger corporate governance.
"Facebook has consistently gambled with the rights and well-being of its more than two billion users -- as well as the company's future -- without adequate consideration of the risks involved," they wrote in a letter.
That future may have arrived.
CNET's Andrew Morse contributed to this report.
First published July 26, 8:04 a.m PT.
Update, 9:04 a.m.: Adds more background on Facebook and investor backlash.
Update, 12:28 p.m. PT: Adds comment from Trillium Asset Management and clarifies that their proposal was submitted in June.
Cambridge Analytica: Everything you need to know about Facebook's data mining scandal.
iHate: CNET looks at how intolerance is taking over the internet.