NY Times has a puff piece on J.K. Rowling and the last two Harry Potter books.

"There are two questions I don't think I've ever been asked and that I should have been asked, if you know what I mean," Rowling said.

She told the gathering they should be asking themselves "not 'why did Harry live' but 'why didn't Voldemort die?' "

The second question they should think about is: "Why didn't Dumbledore kill, or try to kill, Voldemort?" she added, referring to the headmaster of Hogwarts School of Witchcraft and Wizardry.

It's not like people haven't thought about this before. To me, it's one of the principal reasons why I still anticipate getting burned in a big way by Harry Potter in the end--a burning that will be worse than even Star Wars, because I will have read seven children's books to get it.

There just has to be a good reason for these things. We'll see if she's got one. And "Dumbledore IS Voldemort" doesn't count as one. (Neither does "Evil must exist for good to exist.")

The prophecy issue raised in Book Five may be a good start. The fundamental institutional corruption of the wizard world (also raised in Book Five) is another.