&gt; <i>We have no idea how many attacks have been prevented</i><p>Yes, we do. We know ALL of the FBI&#x27;s high profile terrorism cases. Apart from the Tsarnaev brothers, it has been all cases where one or more fools got snared by a provocateur.<p>So unless you believe that there is a secret system of arrest, a secret court that hears terrorism trials, and secret prisons all operating inside the US, we know exactly how effective mass surveillance of the US population has been in preventing terrorism.