kids would be able to hide their drugs a little more effectively, violent gangs would be able to hide weapons, or even conceal them out in the open. Someone could be carrying around a minigun and you might not know it. Divers could get closer to fish, and keep clear of sharks and other dangerous animals, and same for on land, photographers could easily sneak up on that gorilla and take as many photos as they like. Laser tag and paintball just might become a very difficult sport. You could trick people into thinking that you lost all of your teeth in that fight you just got into, or after you stack your bike, you could trick others into thinking that it tore off your arm. it could cover up any details of your face that you don't want others to see... and leave them with gaping wholes. You could pickpocket, loot and be a menace to the rest of the world and noone could stop you.
I'm starting to think that this could be a really bad change, the police would never let people buy them, especially since you could avoid getting your car defected, hide an explosive anywhere, or even hide a drug lab... almost... sense of smell would become an issue there though.
edit: oh, and thermal vision would shatter this ideal in an instant.