Yes, low res cameras might not see the shoe because it's too small. In the same way, a person walking past a car might not notice the show sticking out the bottom because it's too small, so I wouldn't count that as an issue.
Secondly, we can by no means notice every detail in a scene in front of us in one sixtieth of a second, so in the same way different pixels can be analysed and processed over a short period of time.
I think this could be very useful. It's one approach to AI being smarter about not shooting each other in the back, being able to shoot at different parts of the player without having to use multiple traces to see if any part of the player is exposed, realistic visibility issues (fog as John said, as well as foliage, crowds, shadows, and so on).
It could be worth trying in an experimental demo where the player must defeat/avoid/escape one or a few AIs using that system.
Jibb