I actually think its the methods and what they target specificly, civilians, suicide bombs. Its the unknown and things that we are not used to that scares us. The fact that media likes to cover it more then other news is another matter to take into consideration. Other matters as deciease is another thing that scares people, it is also the matter of the likelyness of dying of the "threat" we meet. If there is a bomb blast near you it is bigger chance of getting injured or being killed. Standing besides someone with the flu is less likley to get you killed. Being hit by a car and dieing is a less likley thing then the bomb blast aswell.
The chance of getting killed (what we think, not facts of what really goes on) also the fact that many people might more likley die at the same time then being hit by a car.
The threats that terrorists put out in media is also a big issue I think, makes you feel less "safe".
Thats my thoughts on the matter.
If media stopped brodcasting people that has been targeted by terrorists its more likely that the fear calms down, WTC might also be a reason that is in all peoples heads as a thing assosiated and done by terrorists which makes the word stronger then "flu" will.
An epedemic has about the same effect as terrorism has.
Edit: Just think if a car company would put out ads that cars can be deadly and its effects in a car crash then there would be very few people actually buying a car.
