I have a tendency to borrow books from people and then move to a new city / country / continent without giving them back. I don't even do it on purpose, I just forget about it until it's too late.
No-one's complained so far, but nowadays, I warn people to make a note whenever they lend a book to me. You never know what's going to happen. Might be I spontaneously decide to pack my backs and take other people's stuff with me.