...why are horror/monster/thriller movies so popular?...

I often wonder, just why horror movies are so popular. Most people I know are terrified of these movies. Others, like me, think they rock and are fun. But for the people that are frightened by these films, why do it? What is the thrill of having nightmares, being afraid? What primal need for that drives them? I mean, it's slightly masochistic when you think about it...

What do you guys think?

(And for those of you who LOVE horror films, I have hyperlinked the title of this post to one of the Web's best horror news sites, Bloody-Disgusting! Click and have fun, fellow Council members!)