Someone else has taken the original idea and made them into a security feature for web discussion-boards to prevent spoofing. It's a one-way hash from someone's IP address into a unique picture. Quite a clever idea, I think.
I noticed a few weeks ago when these shapes started showing up on wordpress blogs. It seems they've added it as a standard wordpress plugin option. It will take me a while before I don't do a double-take each time I see them though.