The Sorting Hat seems unlikely. First, how would he get access to it. Also, he'd have to kill someone inside Hogwarts to do it. He did that to create the notebook, but have we heard of anyone else dying way back when that he could have done it?
Also, it would have set up a peculiar incident where Harry called upon the Sorting Hat and withdrew the sword of Gryffyndor to fight Tom Riddle. This essentially pit two parts of Riddle's soul against each other. (And, IIRC, unlike the movie when Harry pulls the sword from the hat, in the book he puts on the hat and reaches for the sword from inside the darkness. Surely, Voldemort's soul, had it been there would have had something to say about that.
As for Harry's scar, that presents a problem. It would explain Voldemort's order that no one kill Harry, but V knows that he must kill Harry and thus a part of himself. Possibly, he's planning to retrieve that piece before killing Harry.
But it seems problematic that V would have made Harry a horcrux. Now the prophecy said that he would leave his mark on him, and so he did. Did he accidentally create a horcrux when he killed Harry mother and was blasted with his own spell? If so, did he know about that creation?
If he did so accidentally, then he would have had to have known that he did it, otherwise, he would've created an eighth piece of his soul. You know.... I'm starting to believe that this is what actually happened, which is why Harry could see V's thought and also see from the perspective of the snake. The snake is another horcrux and the three are connected. Hmmmm, I'm not sure that I like this development and I wonder if I should stop thinking about it because I'll ruin too much of the last book when it finally comes out. (I don't want to figure out too much in advance. Then again, I thought before reading the book that the HBP would be Hagrid, but as soon as I saw it connected with the Potions book, I realized that it wasn't going to be a person showing up with that title in the present. And, of course, I wondered about Snape, because it was a Potions book.)
On an entirely different note: anyone figure out anything about the origin of the name Merope? The names of characters usually mean something. I mean, did anyone not make a connection between Sirius Black and the big, black dog that kept showing up?
TS
Merope: Merope[mer´upE] Pronunciation Key, in Greek mythology. 1 One of the Pleiades. She was the wife of Sisyphus, king of Corinth, and the mother of Glaucus. According to one legend she became the lost Pleiad because of the shame she felt for having married a mortal.
I have one problem with the snake being a horcrux. SHe is with Voldemort when he first appears in GOF. Why couldn't he "resurrect" himself at that point if one of the horcruxes was readily available?
Maybe it's Harry. Remember when Dumbledore is speaking to Harry about his parseltongue ability. He avers that Harry also received other talents and powers from Tom Riddle when he survived the death curse and received the scar.
Riddle wants to become Harry and this might be the penultimate battle!