I think some readers realize they dislike the book for this or that reason--but others simply jump on the bandwagon and find that "sparkly vampires!" is an easy thing to bash. (I always associate it with glitter glue, personally, and perhaps that's why?)[second side note: why can't glitter be un-childish? D:]
...if all the different vampires are running around, I can see why so much research is required. Tell them good luck from me.