When Facebook was getting started, no one used real identity - everything was anonymous or pseudonymous - and I thought that real identity should play a bigger part than it did.

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.

The days of you having a different image for your work friends or co-workers and for the other people you know are probably coming to an end pretty quickly. Having two identities for yourself is an example of a lack of integrity.

There have been misperceptions that we're trying to make all the information open on Facebook, and that's completely false. There are big buckets of information that we recommend that you share with only your friends privately. Then some of the more basic information, we recommend that that's visible to everyone.

Facebook is shaping a broader web. If you look back for the past five or seven years, the story about social networking has really been about getting people connected. But if you look forward for the next five years, I think that the story people are going to remember five years from now isn't how this one site was built; it is how every single service that you use is now going to be better with your friends.

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.