Dreamworks has a tendency to do this. They make a CGI movie and release a trailer for it. The trailer is terrible. The movie ends up being a laugh riot. They really have to fire their trailer guys.
The first move that did this was Over The Hedge. The movie that had just preceded it was Shark Tale, which had a good trailer, and which was also bad. Tragically un-funny at times. So if that one had a good trailer and was bad, Over the Hedge has a bad trailer, so it must be ghastly.
But no! It wasn't! Over the Hedge was actually really funny! Madagascar's trailer made it look hilarious; it wasn't. Flushed Away had a bad trailer, and was good. The trailers for Bee Movie were pretty good and the movie, while not terrible, wasn't really describable as good. Kung Fu Panda? Totally crap trailer. Movie? Fan-freaking-tastic. Monsters Vs. Aliens made the movie look hilarious, and it turned out to be... humorous. And now How to Train Your Dragon. REALLY bad trailers, and the movie is, until Toy Story 3 comes out, the highest-rated film of the year!
What is going on over there?! They make a great film and just think "well, we've got this great film. Why bother with a trailer? Haha! We only need those to trick people into crap movies!" Cue the fat, cigar-smoking fat cats laughing in comfy chairs.
LUCKILY, this may end up being great for audiences. The relationship appears to be holding quite well, meaning that if a trailer makes a move look great, you can rest assured that the movie isn't the slightest bit worth watching.