> I see a hackathon as literally all the worst things about software development compressed in to a single event - practically no planning, very little testing, zero documentation

On the bright side, sometimes this is exactly what's needed. I've seen a hackathon which produced, among other things, a simple technology demo that wasn't meant to see any serious use, but if the company were to develop it normally it would have taken a week or two of planning, bikeshedding and review.

Some people just need alcohol to get over their ideals getting in the way, apparently ;)