SpaceX and Tesla boss Elon Musk has deleted his company's Facebook accounts.
He's perhaps the most high-profile person to take the plunge in the wake of the Cambridge Analytica privacy scandal.
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Brian Acton, co-founder of messaging app WhatsApp, said on Twitter it was time for people to delete their Facebook accounts, using the hashtag #DeleteFacebook.
Mr Musk jokingly asked Mr Acton, "What's Facebook?" before another user suggested the billionaire would delete the SpaceX page if he was "the man".
"I didn't realize there was one. Will do," replied Mr Musk.
When another user pointed out there was also a Facebook page for Tesla, his car company, Mr Musk moved to delete that too.
"Looks lame anyway," he said.
He has yet to delete his personal or company Instagram pages. Instagram is owned by Facebook.
"Instagram's probably ok imo, so long as it stays fairly independent," he tweeted.
"I don't use FB & never have, so don't think I'm some kind of martyr or my companies are taking a huge blow. Also, we don't advertise or pay for endorsements, so... don't care."
When one follower told Mr Musk he didn't have to delete the SpaceX page altogether, Mr Musk told him: "You'll live."
Facebook has yet to respond to Mr Musk's move.
SpaceX has previously streamed launches and landings on its Facebook pages. It's not clear if SpaceX and Tesla have social media employees whose jobs might be threatened.
Mr Musk and Facebook boss Mark Zuckerberg have had minor feuds in the past. Mr Zuckerberg has criticised Mr Musk's regular warnings that artificial intelligence may destroy humanity, while Mr Musk has called Mr Zuckerberg's understanding "limited".
A SpaceX rocket that exploded on launch in 2016 was carrying a Facebook satellite.