People wait until late in their career to give back. But why wait when there is so much to be done?

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.

Don't discount yourself, no matter what you're doing. Everyone has a unique perspective that they can bring to the world.

There are people who are really good managers, people who can manage a big organization, and then there are people who are very analytic or focused on strategy. Those two types don't usually tend to be in the same person. I would put myself much more in the latter camp.

Why are most chess masters under 30?

A lot of the time the experts, the people who are supposed to be able to tell you what to do, will tell you that you can't do something even when you know you can. And a lot of the time it's your friends ... who tell you you can do it.

If the original Facebook was the first five minutes [of a conversation] and the stream was the next 15, what I want to show you today is the rest-the next few hours of a deep engaging conversation.