If you sold the company you co-founded for $19 billion in 2014, it makes sense that four years later you might decide to step down to focus on "collecting rare air-cooled Porsches, working on my cars, and playing ultimate frisbee," as Jan Koum wrote Monday on Facebook. But Koum's exit from WhatsApp, the messaging app purchased by Facebook, is rumored to be a little more acrimonious than that. Media reports suggest friction over privacy and encryption preceded his exit. The Washington Post refers to "broad clashes" between WhatsApp's central tenets—protection of user data is paramount, and "you can still count on absolutely no ads interrupting your communication," the founders wrote in a blog post at the time of the acquisition—and Facebook's way of doing things.
The Post describes Koum and co-founder Brian Acton, who left the company in September, as bending to some degree as Facebook started to grab some WhatsApp user data. But sources say there were disagreements about moves that would make the service more friendly to businesses but could weaken encryption. The Wall Street Journal notes that Koum's childhood was spent in Soviet-era Ukraine, and the experience fostered a commitment to privacy. The monetization factor was reportedly a thorn, too, with Koum remaining allergic to ads as Facebook sought to figure out how to make money off its purchase, which had less than $20 million in revenue when Facebook bought it. The Post calls out a "highly unusual" element of Koum's departure: He's currently the only Facebooker on Facebook's board other than Mark Zuckerberg and Sheryl Sandberg, and he'll reportedly give up that seat as well.