>>Then the you obsess for years over him/her, putting up posters with his/her picture, wasting air time on America's Most Wanted (or whatever), and starting foundations in their name.
>>It's even worse if you can't move on with their lives.
That's true enough as it goes for a sudden disappearance, but I'd think a gradual disappearance would cause much less of a stir. People, after long periods of separation, drop out of contact all the time, and nobody starts up poster campaigns because of it. Phone calls, letters, then... nothing.