I've been to a few hackathons over recent years. On occasion I've found them very useful. Forcing yourself to come up with a good idea that you or a small team can build quickly is a great exercise. They've also helped improve my public speaking and presentation skills when it comes to technical subjects.
I will say that you often see quite dull entries from people attempting to make commercially viable products, and that those entries often do well with the judges. I think the participants get more out of it if they go all out and use their imagination, without worrying about the end result. I'd prefer if the prizes at some hackfests were biased towards creative thinking rather than producing an MVP for a product the hackfest organiser can commercialize. This would also make it less like "work at a weekend."
I will say that you often see quite dull entries from people attempting to make commercially viable products, and that those entries often do well with the judges. I think the participants get more out of it if they go all out and use their imagination, without worrying about the end result. I'd prefer if the prizes at some hackfests were biased towards creative thinking rather than producing an MVP for a product the hackfest organiser can commercialize. This would also make it less like "work at a weekend."