People love photos. Photos originally weren't that big a part of the idea for Facebook, but we just found that people really like them, so we built out this functionality.

Advertising works most effectively when it's in line with what people are already trying to do. And people are trying to communicate in a certain way on Facebook - they share information with their friends, they learn about what their friends are doing - so there's really a whole new opportunity for a new type of advertising model within that.

We want Facebook to be one of the best places people can go to learn how to build stuff.

No one has done a study on this, as far as I can tell, but I think Facebook might be the first place where a large number of people have come out. We didn't create that - society was generally ready for that. I think this is just part of the general trend that we talked about, about society being more open, and I think that's good.

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.

At Facebook, we build tools to help people connect with the people they want and share what they want, and by doing this we are extending people's capacity to build and maintain relationships.