I don't know what information you give newbies now but could you include something about stuff in houses not just being up for grabs?
I befriended a newbie and invited her into my house to have a look around and I was horrified when she started harvesting all the stuff on the floor. I had to point out to her that it's not nice to take other peoples things and she was so embarrassed and started putting it back. I think she thought it had all just spawned there! I still had to replace my meat collector :(
It was a lesson learned, next time I'll have to clarify the point before letting anyone in.
But I'm British! We are known for not saying anything ..... the TV sketch where a couple indulge in noisy and uninhibited sex in a train carriage to the discomfort of the other passengers comes to mind, and no-one says anything until they light up - because of course it's a no-smoking carriage! Maybe I need a sign - "this is a no-nicking house" ;)