WhatsApp Co-Founder Leaving Facebook Amid User Data Disputes

By then, Mr. Koum had also shared his unease over Facebook’s data and privacy policies with others, according to the company executive who has spoken with Mr. Koum. While Mr. Koum personally got along with Mark Zuckerberg, Facebook’s chief executive, he felt the company’s board simply paid lip service to privacy and security concerns he raised, according to the executive.

In particular, the executive said, Mr. Koum was tired from fighting back against pressure from the board throughout 2017 to allow advertisements on WhatsApp.

Facebook did not intend to announce Mr. Koum’s departure until later this week, the person added. Facebook will hold its annual developer conference in San Jose, Calif., on Tuesday and Wednesday and it wanted to first get past the event. But The Post’s report foiled those plans, the executive said.

“Jan and Brian’s departures mean that Facebook, WhatsApp and Instagram are all controlled even more tightly by a single person — Mark Zuckerberg,” said Sandy Parakilas, a former Facebook manager who is now an adviser at The Center for Humane Technology. “This centralized control is bad for the users of all of these products.”

Mr. Koum’s departure was a blow to those at WhatsApp, according to one engineer at the messaging service, who asked not to be identified for fear of retaliation. There had been a certain level of pride within WhatsApp’s team over the dedication to privacy and the departure of their co-founder had left many wondering whether Facebook would now open WhatsApp to tracking user data and, eventually, to ads on its service.

Mr. Zuckerberg said in a comment on Mr. Koum’s Facebook post that he would miss working with Mr. Koum.

“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 centralized systems and put it back in people’s hands,” Mr. Zuckerberg wrote. “Those values will always be at the heart of WhatsApp.”