I could have posted loads of really good theories and things in here, but I havn't had the time, when I look up theories, I use the site I posted earlier, page 17.
And Rowling mentions Chamber of Secrets will play a big part, and little bits in that that are generally over looked will be important. And the site came up with how Riddle, in Chamber of Secrets discussed how Ginny 'poured her soul out into the book, and Riddle put some of his back into Ginny'. Now then chaps, when the book was destoryed, if the 'soul' I am about to talk about wasn't destroyed with it, then we have trouble... That is if Riddle's 'soul' went into Ginny, then Ginny is a Horcrux! Which means she'll have to be killed to defeat Voldemort, which ties in with Rowling's habit to kill loved characters to Harry, and characters Harry just starts to see as close friends, Black as guardian, Ginny as girlfriend. I hated Ginny anyway, and I always wanted Hermione and Harry to be together.