I found a poor noob sleeping in his wooden hut with no locks on his door and all windows on his first floor. So I upgraded his hut to stone, put a small wooden storage behind the door, put a key lock on his door, and put the key in the storage through the window. Now he'll wake up like "WTF...?" I thought that'd be more interesting and mysterious than just logging in like "Oh. Somebody killed me in my sleep and destroyed my shack. What else is new?" That is unless someone finds the key before he wakes up and murders him, but that's not my problem. LOL
I did that once, but don't think they ever came back. I have raided some houses and I always killed them, took what I wanted. However, I usually leave everything else including their sleeping bag and put a wall back up where I knocked it down, unless they were being a jerk on the server which I then destroyed everything.