I'm sure you've heard of the UNIX sticky bit, which is used so that anyone can write a new file to `/tmp`, but without being able to access other files in the s

I'm sure you've heard of the UNIX sticky bit, which is used so that anyone can write a new file to `/tmp`, but without being able to access other files in the same directory. I can certainly imagine the same implementation for contacts (create new contact, see only contacts you have created) and texts (create new text, see only texts you have created).