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.

Helping a billion people connect is amazing, humbling and by far the thing I am most proud of in my life.

I mostly built stuff that I liked.

We are so fortunate that our work in connecting the world through Facebook has given us the ability to give back to our local community, our country and the world -- and to work to improve education, health care and internet access for everyone, to serve our community in San Francisco, we can think of no better place to focus than The General.

Think about what people are doing on Facebook today. They're keeping up with their friends and family, but they're also building an image and identity for themselves, which in a sense is their brand. They're connecting with the audience that they want to connect to. It's almost a disadvantage if you're not on it now.

Find that thing you are super passionate about.

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