Invisibility cloak

A.: There, I put you on 'invisible.'
Mom: Huh?
A.: So that people won't skype you just because the computer's on.
Dad: How did you do that?
A.: I'll show you.
Mom: Why?
A.: Well, Irina just called, and you were having breakfast [and I was blogging about the dairy inquisition you were putting me through].
Mom: But if everyone did that, you'd never know who's online.
A.: You can set it to 'online' if you want people to call you. But sometimes you're online doing stuff and you don't want to deal with the call.
Mom: You could just not answer.
A.: Or you could just not be interrupted by the phone call or risk offending the caller.
Mom: But no one would ever call anyone!
A.: Unless they wanted to be called.
Mom: I don't like it.

Mom was truly unwilling to accept the concept that sometimes, people don't want to be reached, and in that event, they have the right to be invisible.