We started decorating our door on our second cruise and did so on the next five cruises. We had a nice collection of magnets that included signs, characters, pirate stuff, ship logos, etc.
Then on our 8th cruise in 2009, we woke up on our sixth day to find every single thing gone from our door! My daughter had gone down the hall for something and when she came back they were gone. She thought we had removed them to pack! Even the specialty ones that wouldn't matter to anyone else! Everything but one Mickey ear. Our room steward found several of them down the hall strewn about on other people's doors, but I never recovered some of the special glitter ones or my Eeyore ones.
So on our future cruises, we will be putting all our magnets on the INSIDE of our door for our enjoyment!