I haven't got a chance to play bf3 yet. I've been doing mw3 online recently. I found this "infection" style of game on mw3, and I can't get enough. Basically it's a 12-18 player game which is timed, one player is chosen randomly as the "infected". They have five minutes to infect everyone else or they lose. The uninflected get either shotgun/assault rifle/smg/Barrett .50cal bmg and the infected only have knives. Once killed you become infected and infinitely spawn. Reminds me of a zombie kind of situation.