You know how I get when people start bandying this word around. I realize that it is in jest in this thread, so I won't go non-linear this time around.
'Need' used in this manner is to me a word that people use when they want to tell you how to live your life, because what you're doing now bothers them in some way.
"How many X do you need" is code. It means "I think you have too many X, and I want to make it clear that I think you should have less X." Use any replacement value you like for X. They know they can't prevent you from owning X, but they'd really feel much better if you didn't own X, or at least not so much of it. It's a passive-aggressive attempt to stick one's nose in where it does not belong, is what it is.
And they ought to stop it.