In reply to Bob:
>Perhaps the point of terrorism is to create terror not to actually kill.
I agree with you there. They can influence the powers that be and get a stronger hand in any negotiations.
But, there are a lot of others with a vested interest in terrorism and increasing the paranoia.
The media and 'if it bleeds it leads' mentality.
The security services get new toys, more cash new laws.
The military suppliers get more orders for their new toys.
Politicians, get to show how tough on terror they really are.
There are entire industries, that seem to be dependent on there being a war, threat of war or terrorist threat.
From the link you pasted above, regarding 4 deaths per attack, and the actual cost.
"... there is no reason to anticipate that the measures have deterred, foiled or protected against massive casualties in the United States. If the domestic (we leave out overseas) enhanced security measures put into place after 9/11 have saved 100 lives per year in the United States, they would have done so at a cost of $1 billion per saved life. That same money, if invested in a measure that saves lives at a cost of $1 million each—like passive restraints for buses and trucks—would have saved 1,000 times more lives."
Whilst we can't put a price on a human life, its a nice little earner for a lot of people.