Now the playbook is we build AI tools to go find these fake accounts, find coordinated networks of inauthentic activity, and take them down; we make it much harder for anyone to advertise in ways that they shouldn't be.

This social-networking thing takes you to crazy places.

We're a community of a billion-plus people, and the best-selling phones - apart from the iPhone - can sell 10, 20 million. If we did build a phone, we'd only reach 1 or 2 percent of our users. That doesn't do anything awesome for us. We wanted to turn as many phones as possible into 'Facebook phones.' That's what Facebook Home is.

Open Graph is a language for structuring content and sharing that goes on in other apps, and we're continuing to build it out longer term. But we found we need to build more specific experiences around categories like music or movies. Where we've taken the time to build those specific experiences, stuff has gone quite well.

Facebook originally got started around the same time as a bunch of the early smartphones and those platforms got started. So we didn't really get to play any role in developing that platform.

If we're trying to build a world-class News Feed and a world-class messaging product and a world-class search product and a world-class ad system, and invent virtual reality and build drones, I can't write every line of code. I can't write any lines of code.