Do your guests just help themselves?

When I have guests I'm kind of the opposite, I tell them if they're hungry or thirsty, to help themselves. Maybe it was the way I was brought up, or a cultural thing, but I was taught to make guests feel comfortable and 'at home.' Kind of a 'mi casa es su casa' (my home is your home) type philosophy. It probably depends on the guest too, some are more courteous about being a guest in anothers home. There are those who try and take advantage of that, and if I know that specifically about them, I won't extend that type of courtesy. Personally, when I'm a guest at somebody elses house, I always ask first before raiding the fridge, etc. And, I will buy/bring my own soda (or whatever), and snacks so if I've got a munch I don't have to ask, and chip in with extra foods for meals.