Natural epidemics can be extremely large. Intentionally caused epidemics, bioterrorism, would be the largest of all.

I have a particular relationship with Vinod Khosla because he's got a lot of very interesting science-based energy startups.

Vaccines are extremely well tested; their safety is well understood. The false allegations about vaccines causing autism have been disproven. But there are still echoes out there confusing people.

Until we're educating every kid in a fantastic way, until every inner city is cleaned up, there is no shortage of things to do.

Don't let complexity stop you.

The misconception that aid falls straight into the hands of dictators largely stems from the Cold War era.

If your goal is to make the world a better place, one thing you can do is pick a specific challenge that you really care about. Then, learn as much as you can about it and try to volunteer your time to help an organization that is working in this area. While you're doing that, look for creative new ways to use technology to tackle parts of the problem that you come in contact with.