https://www.wired.com/story/chris-cox-leaving-facebook/

Last spring, Chris Cox, the chief product officer of Facebook, was promoted to also oversee WhatsApp, Messenger, and Instagram. It seemed, at the time, almost like succession planning. If Mark Zuckerberg were to ever leave the company, Cox, his longtime confidante, and a representative of the engineering and product side, would be set up to run it.

But Cox announced today that, after 13 years at the company, he’s leaving. “For over a decade, I've been sharing the same message that Mark and I have always believed: Social media's history is not yet written, and its effects are not neutral. It is tied up in the richness and complexity of social life. As its builders, we must endeavor to understand its impact—all the good, and all the bad—and take up the daily work of bending it towards the positive, and towards the good. This is our greatest responsibility,” he wrote.