Also, I had a few thoughts on the Harrycrux theory that I'd like to put on the table for discussion.
1. This was an objection brought up by fernwithy on sane_potter: If Harry is a horcrux, then how could he be the one to defeat Voldemort, since all the horcruxes would have to be destroyed before he could engage Voldemort with any hope of victory? The only answer to this I can think of is that Harry might plan to do something that would destroy Voldemort and himself at the same time.
2. How on earth will Harry figure out he's a horcrux? If Voldemort didn't know, and Dumbledore either didn't know or didn't tell him before he died, how else will he discover this? The other horcruxes will be hard enough to figure out, but they at least might have certain clues that point to them. Harry, OTOH, isn't a special object chosen by LV that might be logically pinpointed from knowledge of his preferences and past. So if the big mystery is that Harry holds a piece of Voldemort's soul--how could Harry ever solve it?