https://www.theguardian.com/technology/2018/mar/23/elon-musk-delete-facebook-spacex-tesla-mark-zuckerberg

In an apparent jab against the embattled social network, Musk joked ‘What’s Facebook?’ before deactivating his companies’ official pages

Elon Musk appeared to join the #DeleteFacebook movement on Friday, taking down official pages for two of his companies, Tesla and SpaceX, after he learned – apparently for the first time – that the pages existed.