Kevin: Good piece looking at location and social networking. I've started using FourSquare recently, and as a Nokia smartphone owner, I suffer from lack of a native app. I know that I'm just starting to scratch the surface of it, but for me, FourSquare is too narrowly pitched. I find the game element artificial. FourSquare has a lot of mindshare at the moment, but for me Twitter has more utility. (Having said that I didn't quite see the utility of Twitter when I first started using it.) I do agree that the promoted tweets based on your location has great potential as a revenue stream for Twitter.