How could a movie with such awesome trailers bomb so badly?

I haven't seen the movie yet, but I've been reading the reviews, and so far, no good. I saw both trailers for it, starting with the fake trailer made for "Grindhouse" and then the official trailer, leaving me thinking, "Awesome! They're making it! And it has KANE HODDER!"

What a disappointment. Is it really as bad as they say it is, or is it even worse?

"Just repeat to yourself, 'It's just a show; I should really just relax.'"