‘What's Facebook?’ Elon Musk quips as he deletes Tesla, SpaceX pages

Tesla's and SpaceX's verified Facebook pages disappeared on Friday, minutes after billionaire founder Elon Musk promised on Twitter to take down the page when challenged by a user.

"Delete SpaceX page on Facebook if you're the man?" a user tweeted to Musk. His response: "I didn't realize there was one. Will do."

Each Facebook page had more than 2.6 million followers.

Musk had begun the exchange by responding to a tweet from WhatsApp co-founder Brian Acton of the #deletefacebook tag.

"What's Facebook?" tweeted Musk, who is more of a Twitter and Instagram guy. He also deleted his personal Facebook page.

Meanwhile, U.S. lawmakers on Friday formally asked Facebook's Mark Zuckerberg to explain at a Washington hearing how 50 million users' data got into the hands of political consultancy Cambridge Analytica.

The world's largest social media network is under growing pressure from governments, investors and advertisers. This follows allegations by a whistleblower that Cambridge Analytica improperly accessed users' information to build profiles on American voters that were later used to help elect U.S. President Donald Trump in 2016.

"The hearing will examine the harvesting and sale of personal information from more than 50 million Facebook users, potentially without their notice or consent and in violation of Facebook policy," chairman Representative Greg Walden, a Republican who chairs the panel, and Frank Pallone, the top Democrat, and other committee leaders wrote in the letter.

A Facebook spokesman confirmed the company had received the letter and was reviewing it, but did not say whether Zuckerberg would agree to testify. The Facebook chief executive apologized on Wednesday for mistakes his company made and promised to restrict developers' access to user information as part of a plan to protect privacy.