In the very beginning, Yelp started as a service where we really didn't think people would write reviews for fun. The whole concept of user-generated content was pretty nascent in 2004.

Starting a company, your success is going to be very dependent on how you adapt. You're going to make decisions, you're going to make bets; most of them are going to turn out to be wrong.

One of the challenges of buying local advertising is, how do you know if it worked? How do you know if it's got value? We're moving toward an e-commerce experience for local, an Amazon-like experience for local.

About every year or two, there is a moment of truth where there's some new development in the marketplace, some new technology, some sort of existential crisis. You just have to be vigilant about looking out for those moments.

Consumers are empowered by Yelp and tools like it: before, when they had a bad experience, they didn't have much recourse. They could fume, but often nothing else other than tell their friends.

Maintaining the trust of the consumer is critical to our business

A lot of what Groupon is generating is demand for something people didn't know they wanted.