Seriously...is there a website for this? I can't get it out of my head - finding your doppelganger would be wicked.
You enter all physical details and several pictures and people browse through looking for people similar to them/their friends. and there's an image matching algorithm too. so it does work automatically, but the major fun is looking. and when the ideal one is found, they text/e=mail you and erm...you have a special bond with another human being - always good right?
On second thought, this should be a Facebook application which uses technology from MyHeritage (where you can find which celebrities you look like) to match you across all profile pictures.
I also actually found my own doppelganger which was quite fulfilling:
a striking example of him can be found here: http://www.les