[Viceroy]

I think the subsequent fear after this attack is greater than other terrorist attacks because the bombers were british citizens. In 9/11 the bombers were of afghan origin and were not permanent residents in the US. This is more akin to when the IRA were planting bombs on mainland Britain. It's the fear that a person could look perfectly normal but could turn on their own soceity.
But the signals that an attack from within our own country have been clear for a long time. The Guantanamo Bay detainees who were fighting against our own troops in afghanistan proved that some misguided muslims do not believe they are part of this country at all. That is what I believe scares people, that the next attackers will more than likely already be here.