The area we define as what Quora's good at is long-form text that's useful over time, and where you care about who wrote the text. Not that you need to be friends with them, just that they're someone trustworthy.

You can go to Pinterest, and they'll get to know who your friends are, but they don't get to know very much about what you've done in the past. They're starting with little information about you, and they have to do this personalization.

When you look at Yahoo Answers, there can be a lot of garbage. But if you're careful about the rules and supporting good contributions, over time you can get better and better, like Wikipedia.

The more questions and answers we get, the more useful Quora is.

We want Quora to last forever, and in order to last forever, it's going to need to have revenue. One of the best things about ads is that you don't need to exclude anyone.

We started off by inviting our friends to use Quora, and then they invited their friends, and it just grew from there.