A similar effect occurs when using infra-red LEDs near the face to prevent video recording. The problem is that many phone cameras now have a UV/IR filter - I can see microphones having a similar setup to improve sound quality in the future.
All CMOS cameras have an IR filter, for reasons that have nothing to do with people using IR LEDs to fool (some) cameras. In fact, removing the IR filter and replacing it with a visible light filter is a cheap way to turn a cheap webcam into a (crappy) night vision camera.
