Well, word from inside the company is that CLOVERFIELD is a giant monster movie, featuring something that's being referred to internally as “The Parasite".

There's also a bit more about the style and what it may actually be about or how it'll work (which considering from the trailer, might be insanely cool).

And what makes this different than any other giant monster movie? Well, as I understand it, most of the film is going to be shot using home video cameras, as if from the point of view of real people who are experiencing an attack on New York. It’s designed as a fairly small picture, all things considered, and right now, they’re working to make sure the script is going to deliver some wild thrills (like an earthquake that levels Manhattan or an oil tanker flipping over by the Statue of Liberty), but that it’s not suddenly going to turn into a giant $150 million movie.