When you want to unfriend someone but either (1) you are too much of a pussy or (2) social convention dictates that you can't. Thus you are stuck with half measure such as: blocking them on Facebook Chat, blocking them from your newsfeed, or putting them on extreme limited profile.
Sister: Grandma added me as a friend on facebook and the first thing she did was write on one of my friends pics that I commented on "Sister you look so beautiful in all of your pictures". I want to unfriend her.
Brother: You can't unfriend her just defacto unfreind her, but her on limited profile.
Guy 1: So remember that bitch I went out with last month. Well I ran into her yesterday and she would not acknowledge my existence.
Guy 2: that sucks what a bitch!
Guy 1: I would have unfriended her but we are both in law school so I am bound to run into her so I guess I am stuck with a defacto unfriend. I have blocked her from chat, and blocked her from my newsfeed.