While I agree with this in theory, where I bump into it in reality is say I respect this wish. So I see you are busy, I go off to do my thing with the intent to say hello to you later, never manage it, then there are hurt feelings because I walked right by and never said hello! This has happened to me so many times. So the question becomes, be rude but make sure you say hi, or be polite but suffer from the wrath of hurt feelings later?

And by the way, the 5th person did not realize there were 4 other people being rude ahead of them. Not excusing the behavior, but still...