This mutating list exists so that the users of the www can decide for themselves which sites are cool to visit and which aren't! I got sick of trying to maintain lists of sites and thus I made it so you now have the freedom to add a site you think rocks, delete a site you think sucks, or just visit a choice made by your peers.
The motivation for doing this is to see how Darwinism works on the www. The idea being that URLs with a lot of information content are "more fit" than URLs which contain nothing but links to other places (and there are too many of these---yet another reason for me to do this) and thus they will be selected for. Given changing environments and competition, URLs will have to continuously evolve in order to be selected constantly.