[ShabbyDoo]

I understand the cultural allure of a single event -- pizza, beer afterward, etc. If a company wants to allow all employees to participate, why not have a demo day every couple of months where teams could present stuff they worked on during that period. People could self-organize partially by their own time availability. Enforcing the time-boxing rules would be hard, but I don't think this is an integral aspect of what makes hackathons a cultural success.