"Astute readers will have noticed that if all one's socks are black, and of the same cut, then surely the maintenance of each relationship isn't important"
Actually no. I used to think like this and brought same style socks for that reason. However as implied by the mention in the article of the apps use of the camera, socks fade, especially black ones, and randomly matching same style black socks will end up with 'pairs' that are very different shades (A slap is waiting for anybody that mentions '50' and 'grey' in reply to this!).
I like this idea.. does need to be quite a bit cheaper though!