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.

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

Right now, with social networks and other tools on the Internet, all of these 500 million people have a way to say what they're thinking and have their voice be heard.

Virtual Reality is really a new communication platform. By feeling truly present, you can share unbounded spaces and experiences with the people in your life. Imagine sharing not just moments with your friends online, but entire experiences and adventures.

Berlin is one of my favorite cities in the world. I feel like the energy is very youthful. It has such an important history, including its recent history of unification.

You grow more when you get more people's perspective.

More than four million businesses have Pages on Facebook that they use to have a dialogue with their customers.