You are talking about the pay it forward groups. They are great but I think that things should be left in someplace like the laundry room and not right outside your door. At Aulani, everyone leaves their stuff in the ice room and that works great. I am not concerned about the alcohol being left. That is actually a bit of a hot topic with one side clutching their pearls saying "think of the children" and the other side saying "you should be responsible for your kids". Personally, I am in the other people are not responsible for your kids category. Kids that are too young to know better should not be out of their parent's sight, and if your teen is one of those that would just pick up some random alcohol and drink it, then they probably should not be out of your sight either. And if Disney becomes the place where you realize your kid is one of those, well then better there, where they won't be driving, then at some friend's house an doing something stupid.
People have been doing this for years and it has never been an issue. There are not a bunch of drunk kids at WDW that found left over alcohol. This is what we call making a mountain out of a mole hill.