That's like saying that JPEGs can never be displayed because information has been lost. The belief that you cannot identify someone from a blurred face is an e

That's like saying that JPEGs can never be displayed because information has been lost. The belief that you cannot identify someone from a blurred face is an extremely strong assumption that is just begging to be demolished using some sufficiently advanced technology. In particular, if you only need to go from a list of 10,000 candidate persons (thanks cellphone mass surveillance) to three or four candidate persons (shoot them all and let god sort it out) then I am think it is fairly that you could do so with more or less existent technology. (essentially, use machine learning to transplant faces from DMV photos into the scene and then redo the blur and select the most likely matches). Think of it this way: if you want to winnow 10k candidates down to four people you need to extract less than 12 bits of entropy. It's not trivial because the scene, pose, lighting, etc. make all your measurements noisy and non-independent.