This Boston bombing could not have taken place if people were not allowed to carry backpacks to events like this. Why does anyone really need a backpack anyway? IMO it would not be asking to much to leave your backpack home. The only time I ever wear one is you know, when I'm going backpacking.
"You have people that have their backpacks with them, a runner may have a hydration pack on them, another person may be coming to watch the race and they may have a backpack," Penza said. "You see them so much, you stop thinking that any of those bags might have explosives."
Marathon Security Practices Scrutinized in Wake of Boston Marathon Explosions - ABC News