I don't KOS, and I have yet to die because of it. Mainly because people are so damn bad at this game. Just never let your guard down, analyze the situation and act accordingly and you'll be fine. Shooting everyone you see is the easy way out. You'll announce your presence to everyone nearby and you'll have the guys friends on your ass. And most of all, it turns the game into a sad death match with the main purpose of boasting your own ego.