I did it once, but I honestly didn't think there was anything wrong with the practice. I'd purchased wine in Tetras at duty free and helped myself. This was on Air Canada. I've noticed on Sunwing and Westjet flights they tell you up front it's not allowed. So sorry AC!!!!

That being said, I'm far too thrifty to pay $6 for a drink, but the fact that you have to use a CC seals the deal for me.