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.

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.

I said a long time ago that Foursquare can make cities better. You have these augmented realities like Foursquare and Twitter and Facebook that provide these virtual nodes and instant feedback from anywhere, adding annotation around a physical places.

Jack Dorsey Quotes