Hmmm! Was the sorting hat actually Gryffindors? I know it says somewhere in the books, but I don't remember. Anyways. that seems like a very interesting idea... The only problem I have with it is that I don't quite understand how Voldemort would have gotten to the hat to make it a horocux. Then again, do you have to actually be by the horocux to make it? I would think so...