Have you ever went to the fridge with a craving for a certain thing and discovered somebody else ate it all? You probably said to yourself, 'hey I was gonna eat that.' Then nothing else looks good. There's just no substitute for what you really wanted.
I can't imagine being in a large family and being able to save anything for yourself to enjoy later. I bet whoever invented the idea of small, personal refrigerators came from a large family..lol.
The caption of the cat above reminded me of an episode at work. We were priviledged to have a lunch room with a fridge, microwave and toaster oven. We all kept food in the fridge and respected each other's stuff as their own. I kept some breakfast sandwiches in the freezer. One morning, I went to get one and they were all gone. Come to find out, the janitorial night crew had helped themselves...aka theft. I think they got fired but I can't say for sure but I did change what I had for breakfast from then on.
If licking your food to call it yours doesn't quite agree with your idea of ettiquite, then I suggest a label maker. Or you can do what my 'only child' upbringing can't quite grasp and SHARE...lol.