Is it? How many attacks has it prevented? This. So now I'm curious and I found this posting by Bruce Schneier at https://www.schneier.com/blog/archives/2008/01

Is it? How many attacks has it prevented? This. So now I'm curious and I found this posting by Bruce Schneier at https://www.schneier.com/blog/archives/2008/01/how_well_see_so.html https://www.schneier.com/blog/archives/2008/01/how_well_see_... which is relevant. He points to some data that really indicates that it just doesn't actually lead to preventing terrorist attacks at all.