It’s all about square pegs and round – whoops, I mean rectangular holes.
If you’ve got a friend or relative who still just doens’t get the whole widescreen / letterbox / pan-and-scan thing, despite you waving your hands and drawing pictures on napkins, here’s a great resource: Stop by VideoGrunt and have them watch episodes 2, 3 and especially 4. These folks are good at showing exactly what’s what and why’s why.
If they still don’t get it, it’s time to give up. 