I generally find that it is accidental team-killing that I am most affiliated with, in my first game of CoD 4 in ages I pulled sniper on backlot and at the start of the game I shot an enemy, but as I shot someone on my team ran through the 1m gap between me and bottom car, he spawned behind me and killed me, not noticing that by that time I had 3 kills to my name and the shot that killed him ended the life of another, later on in the same game it happened again to the same fellow and he was rather mad, but he saw my game before (last live on HQ) and realised it was a mistake, this pretty much sums me up as well, although I always check to see if it was an idiotic teammate or a noobish team killer.