For many reasons of a personal nature I do not drink, and most of the people I play with do not drink while gaming (though if we're at one guy's apartment, he'll have a few glasses of wine, another's he'll have at least one Corona).
One of our players was a bit too heavy of a drinker, but he's a douchebag for many other reasons and thankfully isn't our problem anymore.
The final game of the huge Call of Cthulhu scenario I ran had one person drinking, and that is the major reason I no longer allow my players to drink while I run. I tend to make sure no one drinks themselves into a coma at parties, but while running the game I lost track of individuals beyond the game. She went through an entire bottle of vodka on her own on an empty stomach, managed to derail the game for nearly an hour, insulted and alienated most of her friends, and actually drank herself into the point where she had a severe medical problem and should have been brought to the hospital.
With that in mind, I no longer allow my players to drink when I run. They can do whatever they like when someone else is in charge, but I don't need to be worrying about that when I'm already trying to herd cats through an adventure.
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