non disclosure agreement.
Basically all the big sites, toms hardware, anandtech etc. (the usual suspects) all have the NV40 already, chances are they have already benched em and have a small army of articles ready to publish. But they all signed a legally binding document which prohibits them from posting any information.
Basically all the info we have about both the R420 and the NV40 are leaks from people who have breached this contract.