I don't get it either, so often I am running past an area, and 2 or 3 enemies will spawn as I go by and shoot me in the back...
Yesterday again on Overlord, I had a guy spawn close enough to knife me when he spawned in, this has happened countless times in this game...
Also you can kill 1 or 2 guys in an certain area, and the game will keep spawning player after player right near you
This is a major issue that in my mind is causing a lot of players to leave the game, and why IW is not addressing it is beyond me...