TheOriginalWinger.com has a video of a goalkeeper throwing a ball and hitting a ball boy after the ball boy was a little slow in giving the ball up. I don't know if the ball boy (teenager) said something rude to the keeper, but really, the keeper needs to keep his cool a little better.
What is surprising to me is that the keeper didn't get a red card for violent conduct (because if I was the referee I surely would have shown the red card). Violent conduct does not have to be directed at other players, coaches, the officials, but it can be directed at the fans, ball boys, anyone around.
What a jerk!