I didn't mean to sound condescending or demeaning by my previous post- but it's just that every piece of evidence I can find on the web indicates that this lens mount is metal. Yours is the only one who claims their mount is plastic (aside from pre-release speculation posts made just after the lens was announced last year). Unless you somehow got a prototype they made with a plastic mount or something...?
A picture would really help confirm this. It sounds so unlikely for there to be multiple versions of this lens (especially because it was recently released and a revision in the design is unlikely), and the possibility of a counerfit or a fake seems a little absurd (I have never heard of a faked Nikon lens, although with the recent news about the "faked" Intel i7 CPUs... I guess nothing's too far fetched). I might even suggest a call to Nikon to verify that your plastic mount lens is legit? Again, with respect, something just doesn't add up.
Lastly, just an aside about the hood- the bayonet hood is not necessarily a bad thing, I believe it was partially designed to be like that in the case of a lens drop it will break away from the lens, the act of which will absorb a lot of the fall energy potentially protecting the lens. Kind of like the crumple zones on a car. If you bolted a hood on really securely it might not protect the lens as well from the impact shock. I know the vast majority of modern Nikons use the bayonet or some kind of clip-in style. Only the older lenses and the heavy supertelephotos use the screw style now.
Ruahrc