Dave - I like hackathons. In particular I like the 24 hour constraint. Having to build something in 24 hours (really probably 18 hours), forces me to make decisions, to get to the heart of the problem. Similarly, building something that I know I will only have 2 minutes to demo makes me really focus on what is important. I think the constraints lead to more creativity, just like the Haiku with 17 verses and 3 lines opens the door for whole libraries of verse.
Some more of my thoughts on hackathons here:
http://musicmachinery.com/2012/02/20/hackathons-are-not-nons...