Facebook pages for Tesla and SpaceX disappeared Friday after CEO Elon Musk got dared to delete them on Twitter.

The road to the pages’ surprise demise began when WhatsApp co-founder Brian Acton, who sold the messaging service to Facebook in 2014 for $19 billion, tweeted Wednesday that “It is time. #deletefacebook.”

Acton hasn’t elaborated on his tweet, which appeared to be an expression of disgust over reports that Facebook handed over troves of user data to Cambridge Analytica, a firm that was seeking to tip the 2016 presidential election to Donald Trump.

Musk replied to the tweet on Friday morning, jokingly writing, “What’s Facebook?”

Another Twitter user then jumped in, daring Musk to“Delete SpaceX page on Facebook if you’re the man?”

“I didn’t realize there was one,” Musk replied. “Will do.”

Despite SpaceX’s Facebook page having over 2.6 million followers, Musk claimed he had “literally never seen it even once.”

Another user then posted a photo of Tesla’s Facebook page, suggesting that it should be the next to go. Musk agreed, saying that it “looks lame anyway.”

It’s the latest instance of the rivalry between Musk and Facebook’s Mark Zuckerberg, which began in 2016 when a SpaceX rocket launch failed, resulting in the destruction of one of Facebook’s internet satellites.

Zuckerberg quickly took to Twitter to bemoan “SpaceX’s launch failure,” noting that his satellite “would have provided connectivity to so many entrepreneurs” in Africa.

Musk, who is fond of Twitter and regularly interacts with his 20.5 million followers, is fresh off the approval of an eye-watering pay package that could see him take home as much as $55.8 billion over the next 10 years.

Time will tell if he’ll need those Facebook pages to reach that goal.