If somebody writes a review of a dry cleaner, that piece of content is not wildly viral. It's not like a viral video that can spread across the world in a matter of minutes, so as a result, each market is almost an island unto itself.

Choose something you are passionate about - or a pain point that has affected you and that you feel really needs to be changed.

You have to be very nimble and very open minded. Your success is going to be very dependent on how your adapt.

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

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

There are so many businesses that are succeeding on Yelp that don't pay us a dollar, and we're really excited about that.

The entrepreneurs that really make it are the ones that start with an idea but are ready to change it at a moment's notice.