Mohammed Atta was also a person of interest. This has always been the case and was the case all the way back to 9&#x2F;11, and it illustrates why mass surveillance won&#x27;t stop terror. How do you tell the difference between someone who will <i>actually act</i> and someone who holds beliefs that overlap with terrorist ideologies or who simply talks trash on the Internet and is never going to do anything? Any dragnet will simply drown you in more false positives.<p>Edit: lots of people saw Atta being a POI as a sign of a &quot;let it happen&quot; conspiracy, but the much more likely explanation is that he was on a very long list of watched persons. Being of interest for whatever reason is not a crime (and shouldn&#x27;t be), so there is nothing the FBI or anyone else can do until someone actually does something. Of course then it&#x27;s too late.<p>Police can rarely stop crime unless they happen to luck out and be at exactly the right place at the right time. They can only catch criminals and take them off the street so they can&#x27;t commit more crimes.