It's like a security mechanism for spicy material. What stays in Vegas (defined as a group of individuals) does a better job of staying in Vegas if collocation is a requirement.
Another angle is a groupon type service. Do something fun together, get a coupon for food/drink/another fun activity that unlocks when all members on the group reunite in a month. Create mechanism for 'chaining' to encourage stickiness. People get slight push to maintain friendships they might let otherwise let slip away.
Sure, I see what you're saying ionforce, and thanks for the clarification.
I still don't see the point...Hangover only works when you
1. go to the same place with
2. the same people, and
3.you want to lock content with those people