It doesn't stop anywhere. After the initial quantum leap that you can take something that doesn't belong to you, everything else is just a matter of degree.

Elite travellers must be among the worst of petty pilferers. Some Qantas lounges will ask for your boarding pass before giving you a towel to use the shower. I've forgotten how many towels they told me went walking before they adopted this measure. In the old days these urchins would take the modem cables from the lounges. Qantas even told me that the phones themselves were disappearing.

It's wrong no matter who does it or who they steal it from. But it particularly galls me when it's perpetrated against such a customer-responsive airline as CX. Evidently the best service and the nicest FAs are too good for these glorified cutpurses, and I wouldn't be surprised if some of them are dressed in suits and sport impeccable manners. The most frustrating thing is that almost nothing can be done about it. As some have observed, the airline can't risk making a mistake and offending an honest passenger. What might happen eventually is that the airline will simply stop using these cute pebble shakers. A minor loss, perhaps, but something of what defines CX would be lost.