It's funny you should mention this, and I'll explain why.
I'm a student at Temple University. The other day I was sitting in the computer lab and across from me at another table were a group of students who all seemed to be chatting with each other like they were good friends. The group consisted of one guy and two girls. One of the girls happened to be wearing a Twilight shirt. While I didn't catch all of their conversation, at first it seemed they were discussing a project they were working on. The project had something to do with science. SOMEHOW it came to the point, and I'm not kidding you here, where the girl wearing the Twilight shirt was trying to explain why she thinks vampires would sparkle. From a scientific perspective, that is. I wish I could detail their discussion further but I was only able to hear bits and pieces of their conversation. However the conversation ended with the guy telling the girl that the discussion was a waste of time because vampires aren't real as there is no physical evidence to support their existence. The conversation ended with the girl shaking visibly and saying to the guy, "You don't know they aren't real! What if you met one?" Then she said she had to go and stormed out of the room. After she left the guy said to the remaining girl "that's the problem with those twilight movies and books; they make women hysterical."
Take from that situation what you will. I just found it interesting and thought it related well to the topic of the thread.
As for my personal opinion...well, as someone who absolutely loves fantasy to the point where I'm also a published fantasy author (only two short story excerpts published so far but it's a start, right?) working to make a career out of writing it, my views are a bit mixed. While I'll often lose myself fantasizing about enchanted lands or the discovery of dragons or supernatural abilities, I still recognize that fantasizing too much can be dangerous and stupid. For example, (not that we need one, BUT) if I was so set on the idea of marrying a hot elven princess that I completely removed myself from reality in the attempt to "find" said hot elven princess, I'd pretty much alienate and screw myself over for the rest of my life because my expectations were so high as a result of my fantasizing that I'd miss out on having a wonderful relationship with an actual real person. The same goes for Twilight as people who become infatuated with the romanticism and the character Edward in the novels become so obsessed with finding that "perfect" romantic figure that can only exist in a fantasy, in this case sparkly vampires, that they lose touch of the world around them to the point were they don't even acknowledge the wonderful relationships that they COULD have if they would just stop gushing over fake ones.