Main reason the game is so boring. If there's even the faintest, smallest whiff of a challenge being presented to them, they all leave in a hurry. CoD really needs a ranking system
Edit: Or a leaver penalty that actually matters...in HoN (dota style PC game), if you leave a game, it gets recorded to your account. If you go below a certain "leave" percentage, you can't play "ranked" games anymore; you have to play regular games until you bring your percentage back up. Basically, chronic leavers can only play with other leavers. Wish upon all thats holy that this game implemented something like that.