When is Agent Orange Necessary?

Quickie post that I'll update later on. I pose a question to all of you out there who use AIM (All 99% of you) - when is blocking okay? I mean, surely everyone is familiar with the Golden Rules of Aim. In case you aren't, here's the one I'm specifically talking about:

Blocking someone is about the cruelest thing you can do to them. Worse than murder. So if someone pisses you off, don't block them. Ignore them. Fill them with doubt as to whether you are still at your computer. Blocking is basically the Agent Orange of AIM abuse. Savagely cruel, use only when necessary.



So, having pondered blocking someone, and ultimately being blocked by them, it's made me curious: Just when is blocking someone online okay? If ever??