I think it's unnecessary, added stress and feeds into the "coddled from the cradle" mentality. So your (or my) kid isn't invited to a party- that might sting a little bit but that's the way life goes.
Also, the cost and preparation to host 20+ kids who I don't know is more stress than I want to sign up for! I want to celebrate my child at their party, not worry about entertaining a bunch of stranger's children so I fit in at school.
What are your thoughts on this?