For me personally, it's that I actually do the objectives.
It seems that when I'm watching a door, watching a turret and/or trying to get ahead of the ball carrier for a pass... That there's 4 or 5 other jack offs doing nothing but tunneling their target, then bitch at everyone when an objective gets taken.
That or they're banging away on a tank when a healer is free casting in the back.
Watch your objectives people! You get more valor! More experience! More commendations for a WIN than your little one man crusade.
/end rant