Brian Acton, co-founder of WhatsApp, joined the billionaires’ club when Facebook acquired his mobile messaging app for about US$19 billion four years ago. But that’s not stopping him from telling nearly 30,000 Twitter followers to delete Facebook.

The hashtag #deletefacebook has been trending this week as chief executive officer Mark Zuckerberg and Facebook face an escalating crisis over how data on millions of its users was obtained by Cambridge Analytica, which helped Donald Trump with his U.S. presidential campaign.

Acton co-founded WhatsApp with Jan Koum, who continues to lead the company under Facebook.

Since Facebook’s takeover, Acton has taken a different path, recently backing the Signal Foundation with US$50 million of his personal wealth. The foundation is affiliated with Signal, an encrypted messaging app favoured by privacy advocates like Edward Snowden.

Zuckerberg has remained silent as nearly US$50 billion in Facebook’s market capitalization has been wiped out this week, as investors fear the possibility of more government oversight over social media.