Consider the following, which has been lurking out here since I wrote it in 2004:
It occurs to me that in many ways Santa Claus has evolved into a tool for disillusionment. Consider that, at a certain age, children will believe anything Mommy or Daddy says, just because of the identity of the speaker. But then... The Santa Claus legend just collides too obviously with observable reality in too many ways; it is a SILLY story; there is really no way for a vaguely rational mind to embrace it. And because Santa Claus is often the most significant of folklore beings to children, when they lose him, they tend to lose all.
Now, I was never taught to believe in Santa Claus; they only numinous beings I was ever taught to believe in were those of established Christian mythology. I have COME to believe in fairies and ghosts and phoukas and Valkyries and the the Horned God and even more obscure things like Honor and Courage and Nobility, and will continue to believe in them in the face of all argument to the contrary, because all of them have places to HIDE in the rational world.
This is the reason, ultimately, that I both harass and pity atheists; they have chosen to live in a world without any of these things, a world in which Tinker Bell is an impossibility and Don Quixote an absurdity. I look at such people, and wonder how they could have chosen to be so blind, and am forced to mock them-- because otherwise I weep.
I grew up believing that magic was possible, but that I would probably never see it. I am grateful for both halves of that equation; I am glad for both the ability to believe, and the deep rooted skepticism, that this gave me. I WANT to believe; I enjoy believing; it's FUN. But I do not do it easily, and that is a great advantage when it comes to preserving that oh-so-necessary illusion of sanity.