To be simple, I think that after 9/11, there could be any type of terrorism-sounding alert and NY would be up in a frenzy.  It's the effect of what happened, and it's probably a good thing.  People need to feel safe, security needs to be tight, and you never know whether someone is going to try something again.  Caution isn't always a bad thing.  In Israel, I know it prevents terrorist attacks... they need to do the same in America.