IntoMobile: A new Apple patent application US20100039530 reveals that Apple is not satisfied by image quality consistency among camera modules:
"Similar cameras manufactured on similar product lines may operate non-uniformly. For example manufacturing variations may result in variations in response to external stimuli, such as ambient light. Such variations in camera responses may produce a non-uniformity in images rendered by digital cameras of the same type, consequently, leading to an inconsistent product performance and to variations in product lines(s)."
So the company tries to patent calibration of the camera modules.
Thanks to S.S. for the link!