One thing I have reflected on is that when I started Facebook, the mission of connecting the world was not controversial. It was kind of as if it was a default assumption that people had - every year the world got more connected - and that seems like the direction that things were heading in.

Connecting the world is really important, and that is something that we want to do. That is why Facebook is here on this planet.

I updated my grilling app, iGrill, today and it now has Facebook integration that lets you see what other people are grilling right now around the world. Awesome.

A lot of times, I run a thought experiment: 'If I were not at Facebook, what would I be doing to make the world more open?'

After launching the first version of Facebook for a few thousand users, we would discuss how this should be built for the world. It wasn't even a thought that maybe it could be us. We always thought it would be someone else doing it.

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.