Slightly off topic but somewhat related. On a recent AA flight in the US in First, I've stored my backpack in the overhead locker above my seat. A late boarder with an oversize bag couldn't squeeze the bag in above me despite several rearranging and ramming techniques. I politely asked her to be a bit more careful as there were breakables in my bag.
Very shortly after she decided to remove my backpack and was heading towards the front with it, to which I said "Excuse me that is my bag" she responded with, "Do you mind?". "Yes I do mind, that is my bag leave it alone."
For what it's worth, she then found room above her seat for her bag.