Jan Koum, founder of the communications app WhatsApp, sold to Facebook in 2014 for a hard-to-turn-down $19 billion, has walked out following disagreements over plans to water down WhatsApp's end-to-end encryption.
WhatsApp implemented end-to-end encryption between 2014 and 2016 in response to pressure from privacy groups.
However, encryption also prevents Facebook from using technology to scan messages for the purpose of injecting targeted advertising at users - similar to the way in which Google scans messages in Gmail for the purpose of advertising.
And Facebook executives believed that weakening encryption would also make it easier for businesses to use its tools.
According to reports, it was these tensions at an executive level that instigated the Ukrainian-American billionaire's departure from the company. Koum trousered around $7.5 billion from the sale of WhatsApp to Facebook in 2014. His fortune is now estimate by Forbes at $9.1 billion.
In addition to the weakening of encryption, WhatsApp executives were also reportedly opposed to Facebook plans to use WhatsApp data to create user profiles that could be unified across multiple Facebook-run platforms. These would then be used for targeting advertising or data mining.
According to The Washington Post, continued conflicts with Facebook's approach to privacy wore Koum down and cumulating with him deciding to quit and to sell off his Facebook stock options.
Koum later publically announced that he was quitting WhatsApp on Facebook, but didn't reveal the reasons why.
"I'm leaving at a time when people are using WhatsApp in more ways than I could have imagined. The team is stronger than ever and it'll continue to do amazing things.
"I'm taking some time off to do things I enjoy outside of technology, such as collecting rare air-cooled Porsches, working on my cars and playing ultimate frisbee. And I'll still be cheering WhatsApp on - just from the outside," he wrote.
Facebook, though, has remained tight-lipped over the claims, although CEO Mark Zuckerberg wrote in response that he would "miss working so closely" with Koum.
He continued: "I'm grateful for everything you've done to help connect the world, and for everything you've taught me, including about encryption and its ability to take power from centralised systems and put it back in people's hands. Those values will always be at the heart of WhatsApp."
Cotton seedling freezes to death as Chang'e-4 shuts down for the Moon's 14-day lunar night
Fortnite easily out-earns PUBG, Assassin's Creed Odyssey and Red Dead Redemption 2 in 2018
Meteor showers as a service will be visible for about 100 kilometres in all directions
Saturn's rings only formed in the past 100 million years, suggests analysis of Cassini space probe data
New findings contradict conventional belief that Saturn's rings were formed along with the planet about 4.5 billion years ago