Building a mission and building a business go hand in hand. The primary thing that excites me is the mission. But we have always had a healthy understanding that we need to do both.

It's really easy to have a nice philosophy about openness, but moving the world in that direction is a different thing. It requires both understanding where you want to go and being pragmatic about getting there.

The thing I really care about is the mission, making the world open.

It's a juicy thing to say we're building a phone, which is why people want to write about it. But it's so clearly the wrong strategy for us.

We are a mission-driven company. In order to do this, we have to build a great team. And in order to do that, you need people to know they can make a bunch of money. So we need a business model to make a lot of money.

Facebook is inherently viral. There are lots of sites that include a contact importer, and for lots of them it doesn't really make sense. For Facebook it fits so well. It wasn't until a few years in that we started building some tools that made it easier to import friends to the site. That was a huge thing that spiked growth.