On mobile, what are the core apps? It's basically messaging, mapping and review data.

There is this cat and mouse game that plays out over time where our team comes up with new and interesting ideas to identify content that we shouldn't recommend, and over time people are constantly probing that, trying to figure out how can they get around that and get a better reputation on Yelp.

Yelp is in a very nice spot: local data, and especially review data, is one of the killer apps on mobile phones.

Maintaining the trust of the consumer is critical to our business

When Yelp first took off, our rankings on Google would fluctuate wildly.

In early 2008, it was confirmed that there would be an opportunity to build applications for the iPhone. We were fortunate enough to make the right call on that: to bet early, to put resources into it and have a pretty good application in the store at the moment when it opened.

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.