If you have not read Dave McClure's thoughts on the 500 Startups business model, stop now, and go read it.
If you are maybe looking for a bit of light reading that explains the whole theory, culture and practice of startups and why he does what he does, instead, go to his slide presentation given at #sosummit, which I will embed here.
There is much more you need to know, of course, but not much more. Our Microsoft Innovation Center team is in Rio right now, sitting in on discussions like this, participating in a long series of conversations about the model for working with startups.