When our daughter graduated from H.S. we tried to only send invitations to people she, or we, knew very well. We ended up hearing from a couple of people who were hurt that they didn't receive invitations. I really don't know what's best. If everyone followed Miss Manners' advice and only felt obligated to send a congratulatory card, that would fix it. But then I believe the world would be a better place if everyone followed Miss Manners' advice, period.