Yes, but in real life we don't have ways of broadcasting to this ever-changing landscape. In fact, we tolerate quite a bit of collateral damage: you tell your brother something in confidence and he goes and tells your mother.

Socially, yes, this is insufficient. But this isn't really about social reality, it's a technical solution to boredom, which means people enjoy putting work in to manage their friends. It's the whole reason they're there.