I fucking knew someone was going to do dead pixel camera tracking at some point.
Let's say your camera has a dead pixel in the sensor. I've seen this happen ever since digital cameras were a thing. It's just a white spot on every single photo taken with the camera, same color, same spot every single time. By detecting these you can see which actual camera was used to take other photos. The idea with the patent seems to be to use these to identify people in the photos taken with the same camera, then make connections between those people. This has a very high level of certainty as the people would have to physically be in front of the same camera at some point. Most people don't even notice these dead pixels. Solutions: always crop, never show max-resolution photos, use software to eliminate these.
Also, it should go without saying that someone should be looking for dead pixels in all of Q's photos. It's possible.