Hackathons are events where ideas are born and are quickly laid to rest. I'm glad there's some encouragement to work on existing projects, especially on projects that have a civic focus.
It's a shame too. We get all sorts of sponsors and spend a lot of time promoting an event that supposedly benefits the community, but did we really accomplish anything if we just let it drop? Maybe the idea wasn't the most greatest in the world, but now that you've had a few months to think about what you could have done better... pivot.