If someone is someone you want to ignore, or perhaps a better word being don't have enough time to get to know, you simply 'de-friend' them because it's a good idea to give attention and energies to those you consider to be a true friend, and let other relationships exist in the in-between world of acquaintance-ship, or business relations. That's a truthful way of doing it vs. creating a complicated hierarchy of virtual relationships that you want to edit partially or entirely out of your life. Why has Facebook turned us into fourth graders? What's next, a rating system?
Whatever happened to the simplicity of "friend or foe," and a world where you had less choices in terms of circles you could be part of, yet more assurances? Today it seems like if we decide to opt-into virtual and social networking we give ourselves the burden of having to establish a structure of community within that framework, or in other words some semblance of a reality.