You hesitate at close friends staying at your place? They probably are not that close of friends. I'd toss the keys to plenty of relatively close friends with a "hey make sure the cat doesn't sneak out, he's a bastard like that. Have a good weekend, feel free to raid the fridge"
We probably just have different views of personal space. I don't like people in my private spaces; it is hard enough when I am there, and even worse when I am not.
It isn't about closeness to the person; I wouldn't be super comfortable with my best friend, my family, doesn't matter.
