Well, I thought it was a good read anyway.
http://www.linquist.net/motorsports/tech/mirrors/
I had never previously given my mirrors much thought. I've always adjusted mine so that the side of the car is still seen on the very edge of each mirror.... ever so slightly. However, as this site demonstrates, even doing that you're still duplicating some of the image available in your rear view mirror.
The idea is to set the mirrors even further out, so that they pick up where your rear view drops off. Makes a lot of sense... just never really thought about it.