I was flying on Sri Lankan UL from CMB to PVG in business class. Suddenly on the TV screen popped up a warning to be careful of your personal belongings. First time I have seen it on an airline.
I asked the crew and they told me on that route passengers steal lot of stuff. I said even in business class? They said yes. They even change shirts so they don't look as before.
I have seen passengers try to take pillows from others while the passenger is out of his seat and I have stopped it every time it happened near me by pointing out that there was a passenger sitting in that particular seat.