This isn't limited to hackathons, and to be fair the title is fairly click-baity. I remember seeing a page here on hn listing 1001 great ideas. So if you are o

This isn't limited to hackathons, and to be fair the title is fairly click-baity. I remember seeing a page here on hn listing 1001 great ideas. So if you are out of ideas, then just pick one from there and adapt it to a problem you have identified. There are an endless number of ideas you can come up with that combine some of your domain knowledge with a problem you can identify in your local community. I was just reading an article about pot holes in Oslo. How about an app that lets you quickly log a pot hole. Or use the accelerometer to identify pot holes and warn other users. Or let you plan a bike route to avoid pot holes. Everyone is capable of coming up with ideas. Just because they come from a developer doesn't make them any better than coming from a non-developer. Then again lots of terrible ideas come from both devs and non-devs. The upside for the developer is that they can evaluate the complexity of an idea much better than non-devs and can make a nice little demo to show others.