Holding a voting machine hackathon
I suppose that's fine if your voting machines are open source, but if you try to keep them under wraps you probably just make them easier to hack. If you wanted to hack voting machines, you might participate in the hackathon to get access to them, but keep any holes you find to yourself and tell the organizer "wow, these are very secure!"
Then you have the knowledge to hack into them later using the holes you found and didn't tell them about, which left them unfixed.
Biting the hand that feeds IT
