Looks like the folks at HobbyKing has fully embraced the Multicopter revolution. To that end, they've created a contest for 2012, the goal of which is to lift our favourite beverages, BEER! They don't say whether the beer cans need to be full or empty. I think the goal is to lift as much weight as possible. So there may be the obvious incentive of lifting many empty beer cans, versus smaller number sadly full cans.
Link to contest is here.