Great list indeed.. And the key points are focusing on a niche (cheap, easy, close, ...) before expanding. BUT even though Foursquare did that in New York to begin with, the speed of expansion afterwards is important too. Foursquare went from 1 city to 100+ in a bit less than a year opening slots of new cities every second month or so. As Groupon did that in a shorter period of time. The conclusion simply being (i guess) : once your model (product, business) is proven locally on a niche, don't wast time and get global fast.