A ton of it is muddled in politics and branding. I have yet to see many "big, scalable" companies come out of the ones that have been hosted.
Getting developers is tough, and being the only developer on the organizing team selling the event to other developers when they had free, more legit hackathons made it an insane choice.
I will say that events that Code for America have hosted have been nice. They seem as far as I can tell trying to change something a little more real than the "Uber for X".
Has anyone here tried both? I personally like the style of Branch a lot more, and movement seemed a lot smoother.