Rattled by scandals involving fake news, data-sharing scandal and privacy, and free speech questions, Facebook stock tumbled roughly 20 percent after hours on Wednesday in the US and the next day.

The social network released earnings showing that its user growth has stalled; its daily active users grew to 1.47 billion in the second quarter, but there was no user growth in the US and Canada and a drop of 3 million users in Europe.   Facebook's revenue increased 42 percent to US$13.2 Billion, but that missed the $13.3 Billion that Wall Street wanted to see. 

The stock plunged after the company told investors that it expects revenue growth to slow for the rest of the year.

"Our total revenue-growth rates will continue to decelerate in the second half of 2018, and we expect our revenue-growth rates to decline by high-single-digit percentages from prior quarters sequentially in both Q3 and Q4," said Chief Financial Officer David Wehner, who warned that Facebook still expects expenses to grow 50 to 60 percent from last year.

Mark Zuckerberg's personal fortune tumbled by $16.8 Billion.

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The problems, especially the loss of European users, are attributable to the Cambridge Analytica scandal, in which the conservative pollster breached 87 million Facebook profiles.  That prompted the European Union to introduce strict data protection legislation.

Facebook was also forced to devote vast sums on improving data security and increased policing of the site after Zuckerberg admitted to Congress that the company had been too slow to react to Russia's attack on the 2016 US presidential election.