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.
Shares in Facebook fell about 8% in after hours trade in NY. News that the data firm accessed information from as many as 87 million Facebook (FB) users without their permission broke in the final weeks of the first quarter.
Instagram has grown to 1 billion monthly users from 600 million in late 2016, while Facebook's two messaging apps, Messenger and WhatsApp have each reported well over 1 billion monthly users.
Wehner attributed the poor revenue expectations to several factors: currency headwinds, the R&D cost of building and promoting new experiences, and impacts on Facebook's business from new privacy regimens in Europe due to GDPR.
"Our community and business continue to grow quickly", Facbook CEO Mark Zuckerberg said in a statement. Its total user count represents an 11 percent increase over the year-ago period.
The company beat the profit forecast, with $1.74 per-share earnings.
Also alarming to investors: Facebook's growth is slowing with users in some of its most lucrative markets.
Facebook reported on Wednesday that growth in digital advertising sales and in the number of its users had decelerated in the second quarter.
Daily and monthly active users in Europe fell for the first time, to 279 million from 282 million and to 376 million from 377 million, respectively.
Instagram is expected to account for 18 per cent of Facebook's revenue this year and 23 per cent next year, according to research firm EMarketer.
Facebook's shares recovered somewhat after the call. Revenue from these regions, however, is far below what Facebook rakes in from the USA and Europe.
"This [Instagram] has been a story of great innovation and product execution", praised Zuckerberg, who added that Facebook's sprawling infrastructure enabled Instagram to scale twice as fast to where it is now with 1 billion monthly active users.
Facebook said the European privacy rules, called General Data Protection Regulation, or GDPR, did not have a big effect on the quarter's revenue, but also noted that they were only in effect for about a month before the quarter ended. So far, WhatsApp doesn't show ads, and its founders Jan Koum and Brian Acton left Facebook amid disagreements over advertising and other issues.
Analyst Ross Sandler with Barclays asked if revenue growth was set to drop to "around 20% by the fourth quarter of this year".
But revenue - up 42 percent to $13.23 billion- was slightly below the $13.34 that Wall Street was expecting.
The threat of additional privacy regulatory setbacks remains a concern, according to analysts.
Facebook has shown that it can not sail forever forward while facing various storms, including Cambridge Analytica and the Russian government's use of the social media platform to sow divisions amongst Americans during the 2016 presidential campaign.