I have the same issue, but only at the usb cover.

Seems that the Black N9 has a matte coating over the black PC. The coating seems to have 2 layers, the outter black and the inner gray..

When the whole coating has worn off you will feel the real PC which is paint throughly in black.

So don't worry, Nokia has applied another layer of protection to the real body.

So in conclusion, the N9 housings are NOT FAKE, the PC is not painted, but rather matte-coated (the cyan, magenta and white does not have this matte coat)