There is a good reason why good computer science doesn't come out of a hackathon type setting. Good computer science that shows us something new really requires at least 6 months of solid work to get up to date on some of the research in a narrow field. Even after over 6 months of reading academic papers I realized I would have to keep my focus narrow because some of the other things I thought about would have required much more reading.

In a short period of time you can't really hope to produce anything meaningful in new ground, you can however produce interesting little ideas and mashups which is what hackathon like events tend to focus on.