It's a matter of invitations versus context. Twitter is really good at providing context, like, I''m having coffee at Third Rail Coffee.' Foursquare is about invitations to places. In this respect Foursquare has started to replace Yelp for me.

As CEO, my main job is editor-in-chief.

'Luck' is recognizing when the situation encourages build out and execution.

The idea of Twitter started with me working in dispatch since I was 15 years old, where taxi cabs or firetrucks would broadcast where they were and what they were doing.

Everyone has an idea, but it's really about executing the idea and attracting other people to help you with the idea.

I am someone who tweets about what I have for breakfast, what I have for lunch, what I have for dinner, and for 99.99999 percent of the world, it's useless. It's meaningless. But for my mother, she loves it.

I think Twitter is best when it sparks conversations elsewhere. To use YouTube and Facebook and all the tools we have available to us today to respond and also promote and answer and engage is awesome.