The major way you earn experience points in Velvet Assassin is by swiping mundane items from the Nazis while you're trying to kill their dudes and sabotage their stuff. This seems to elevate the activity from a slight diversion as a mini-game to a central part of what you do in the game. This is screwy, because the activity doesn't make a lot of sense. Why does stealing a Nazi telescope make me better at sneaking instead of, you know, sneaking to get better at sneaking?
I hate completing a mission and seeing I missed two out of ten possible collectible bits of junk. It means you've missed some XP, and there's no way to go back and get it. You've effectively gimped your character a little bit, forever. I can't tell if the game designer tuned the difficulty of the game so that these are a mild bonus for eagle-eyed players, or if the game will later become punishingly hard without them.