Anyway, the real thing I wanted to post about: The theme of choices, and the apparent confusion about how Tom's background pre-disposed him to evil and presumably so did Draco's, etc. People think this is a contradiction somehow. I disagree.
Most of the conversation about how it's a betrayal of the theme of "choices" to have Tom be more or less wicked at the age of eleven seems to focus around Dumbledore's line about choices being more important than abilities.
Except that that's not what Dumbledore says.
In CoS, chapter 18, Dumbledore says, "It is our choices, Harry, that show what we truly are, far more than our abilities."
Dumbledore does not say, "Our choices make us who we are." He does not say, "Everything we do is about free will" or "There is no inborn tendency to any specific pattern of choices."
He says our choices show what we truly are.
This comes off at first sounding like a minor quibbling about semantics, but I think it has much larger implications about the nature of identity as seen in the books, especially when combined with things like the Sorting Hat (which is never wrong and sorts people by personality traits at the age of eleven), the doublings of characters--Harry the good neglected child with Tom the bad one; Remus the good werewolf with Fenrir the bad one; etc.
This isn't a betrayal of the concept of "choice" as Dumbledore uses the word in the CoS scene. What Dumbledore is trying to show Harry is not that Tom made different choices (which is pretty obvious), but that those choices indicate a big difference between the two boys--a difference which is there all the time, at the root of things, which is demonstrated by the choices each of them makes. In a nurture-only view of the world, Tom and Harry should have made the same sorts of choices, but there we see them, at the age of eleven--Harry's first instinct is to assume Hagrid has made some sort of mistake, while Tom's is to start spinning grandiose fantasies about his power and brag to Dumbledore about the things he's already figured out he can do. By the time we get to the Sorting Hat, Harry has chosen to reject Slytherin, which has been presented to him by Malfoy as representative of bigotry and snobbery, and throw in his lot with people like the Weasleys, who are very down-to-earth. Given Tom's behavior and interest in seeing himself as a class above other people, Malfoy's approach probably would have appealed to him, and he would have wished for Slytherin because of it.
Now, whether or not this is an accurate state of affairs in the real world, or an offensive notion, or whatever... there are a lot of ways to look at it. I'm just pointing out that it's not a contradiction of anything Dumbledore said about choices.