It's such an odd question, b/c that's what happens when families go to sleep.
My husband climbed out of his crib and hid, at 9 months. His mom came in to the room the next morning and freaked out until she heard him. One doesn't think of sleeptime as being unsupervised, but it is, and of course families have to sleep.
I had a friend who was caring for a child that wasn't hers, and he had behavioural problems. He would wander the house and beat up on the other kids. They finally got fed up with it and put a lock on the outside of his door. He told someone, and they were severely warned that locks on the outside of doors weren't allowed. So they just had to let this boy beat up their children and wander their home, b/c they couldn't have someone awake 24/7. There was no winning.
My son sometimes wakes up before I'm awake, and he brings toys into the bed, he looks at books, he talks to me, shoves action figures under me, and so on. It's hilarious, seeing what all he does while I'm dozing. One day he was feeling a little spooked by something, and put a ring of "weapons" around me...Lego "blasters", his light saber, a stick, and so on. I was boobytrapped in case someone tried to get me, I guess.
My brother and I used to get up earlier than my hard working single mom, and she had a whole thing set out for us. Little Tupperware pitchers of milk (so we didn't have to deal with the gallon container), cereal in Tupperware, bowls set out, and so on. We knew the rules, we followed the rules. Of course it was a teensy house and I'm sure she could hear us even while snoozing, but she was getting extra rest.
But I'm sure there are bad situations, too.
I can't vote b/c there are too many variables.