That's my impression. The world is full of nanotech factories - we call them bacteria. They assemble molecules as necessary, but they don't do it the way it's

That's my impression. The world is full of nanotech factories - we call them bacteria. They assemble molecules as necessary, but they don't do it the way it's done on the macro scale, because the macro-scale model doesn't transfer to interaction at the nano scale. If the grey goo scenario was possible, I suspect it would have evolved as a life form.