You set a scenario for a potential disaster but what has surveillance done to protect those in times square on new year. This question has no answer and the answer if it exists is NOT something a democracy has access to.

So if surveillance is an answer to a potential terror plot then what needs to be known is whether it can actually be effective. Terror plots are not the norm of human life. They are feared more because we humans are designed by nature to be afraid first when we see a lion, run away and think later. If we stood there contemplating the possibility of of having a deep conversation with that lion that lion would have managed to have a meal deep in its stomach. Thought is very low on mother nature's agenda. Even other great apes don't comment here! Basically we are more afraid of the danger because we are primed to be so. I guess what I'm trying to say is that while fear is a danger is a logical thing it shouldn't be the only thing to consider when deciding on surveillance. Currently it is the only reason presented to the public and it is not good enough on its own.