One more thing

I just thought of something. Twilight fans might be overwhelmingly female and largely teenage, but Sarah Palin fans are middle-aged white men, and she gets quite a lot of media backlash. Say what you like about changing demographics and whatnot, but last time I checked middle-aged white men still pretty much ruled the world.

So actually the thing they have in common is strength of devotion combined with the poor quality of the underlying product.