I agree with martinoma, I was just at a hackathon this past weekend, and everyone signed up to have fun rather than compete for prize money/gadgets. We didn't know about the prizes until the winners were announced, nonetheless about 40-50 people showed up, and the prizes ended up being pretty cool gadgets, of which included 3 rasberry pi's. The theme of the hackathon was "Interacting with the real world." So we had to fiddle around more with hardware and less with the software. It was my first hackathon and I really enjoyed it, looking forward to attending many more in the future, primarily to have fun and meet people with similar interests.