Twilight on "Challenged Book" List. But why?

MSN tells me that the Twilight books are some of the most often challenged books. Reasons: sexual content, the blood-drinking thing etc. How about the fact they are just, um, terrible? How about the fact that Meyers can't seem to put an intelligent sentence together? Or the fact that she finds maybe three unimaginative metaphors concerning her characters and then just endlessly recycles them? (ex: apparently the only wildly creative thing about Edward is that his skin is "like ice".... wow, Stephanie, let's try to find a MORE obviously cold thing on the planet)