Find that thing you are super passionate about. A lot of founding principles of Facebook are that if people have access to more information and are more connected, it will make the world better; people will have more understanding, more empathy. That’s the guiding principle for me. On hard days, I really just step back, and that’s the thing that keeps me going.

I think that more flow of information, the ability to stay connected to more people makes people more effective as people. And I mean, that's true socially. It makes you have more fun, right. It feels better to be more connected to all these people. You have a richer life.

Just because you can build a machine that is better than a person at something doesn't mean that it is going to have the ability to learn new domains or connect different types of information or context to do superhuman things. This is critically important to appreciate.

Look at the way celebrities and politicians are using Facebook already. When Ashton Kutcher posts a video, he gets hundreds of pieces of feedback. Maybe he doesn't have time to read them all or respond to them all, but he's getting good feedback and getting a good sense of how people are thinking about that and maybe can respond to some of it.

The primary things that people do on the Facebook is they use it to share with their friends and the people around them and their community, and they use it to keep in touch with people.

Of course the Silicon Valley is unique and Berlin is not yet comparable. But of all the different cities that are building a startup infrastructure, Berlin is the one with the most similar energy.

Providing the best photo sharing experience is one reason why so many people love Facebook and we knew it would be worth bringing these two companies together.