I'm obsessed with the idea of social TV.
One of the biggest hurdles about Foursquare is you need to remember to use it.
I keep a notebook in my pocket, and I write down all the stuff we could ever do with Foursquare.
Don't let people tell you your ideas won't work.
Forget about where you want to be and go out and build stuff. Dodgeball came from being bored at work... things happen because you make them happen. Stop sketching, and start building.
What we're starting to see is that the best apps tend to be the simplest, the easiest to use and the fastest to use.