I've never been to a PennApps Hackathon, but from what you describe (1000+ people), I'd imagine that it's pretty much impossible for event organizers to prevent this. I think the key here is the 'left unattended' part of the scenario. The solution would be to tell the teams not to leave the equipment unattended. It's unfortunate, but a reality of life (even at a Hackathon with a great community); There are bad people out there. I've been to quite a few Hackathon / Startup Events (granted, much smaller), but I've never left my equipment unattended. I consider it a part of Teamwork, Communication, and Organization. If someone from the Team isn't there to watch the equipment, then it comes with me or gets packed up and put away somewhere safe.