though the token gathering idea sounds cool, when you think about putting it on on a grand scale, it doesn't work so well...
at PAX 09, there was the challenge button game. everyone got 2 buttons in their swag bags, and had to play some sort of game against other people with buttons to with a button from them. The thing that happened was very quickly people ravaged the swag bags and such. Now I know in your scenario, you'd be having the handheld people handing them out, but they already have enough to do. not to mention, people can just request annother bag, etc. etc.
One thing that we have to keep in mind is how abuseable the system is. In a perfect world, everyone would know what's going on, and what the rules are, and obey them. But in reality, some people won't know the rules, or what's going on, and be left out, or accidentally (or intentionally) break the rules.
Yeah, we can think that everyone at PAX will follow Wheaton's Law, but in actuality, there will always be some that don't. And the innevitability is that we have to plan for those who don't.