I can remember pelting the broncos bus with snowballs in 2005 and the police escort as well....oh to be young, drunk and invincible.
I agree that it's not part of the game, and have no issue with security picking out the 100's of violators and kicking them out. That said, to expect that it won't happen or to penalize a team is foolish. If the league has an issue with safety, the course should be to stop play and/or pull players from the field. After that the, crowd will enforce itself.