I disagree. There is a lot of evidence that terrorist groups are incredibly ineffective. Not just recent attacks in the US, but statistics world wide and through all of history. Gwern wrote a detailed essay on how incompetent terrorist groups are: <a href="http:&#x2F;&#x2F;www.gwern.net&#x2F;Terrorism%20is%20not%20Effective" rel="nofollow">http:&#x2F;&#x2F;www.gwern.net&#x2F;Terrorism%20is%20not%20Effective</a><p>&gt;9&#x2F;11, the crowning incident of terrorism in those centuries, was equaled by just 29 days of car accidents in the US - and 9&#x2F;11 was only <i>accidentally</i> that successful! 9&#x2F;11 is also a sterling example of the availability bias: besides it, how many attacks could the best informed Western citizen name? Perhaps a score, on a good day, if they have a good memory; inasmuch as the MIPT database records &gt;19,000 just 1968-2004, it’s clear that terrifyingly exceptional terrorist attacks are just that. Remarkably, it seems that it is <i>unusual</i> for terrorist attacks to injure even a single person; the MIPT database puts the number of such attacks at <i>35% of all attacks</i>. Certainly the post-9&#x2F;11 record would seem to indicate it was a fluke...<p>&gt;Many terrorist organizations keep very detailed financial records (consider the troves of data seized from Al-Qaeda-in-Iraq, from Bin Laden’s safehouse, or Al Qaeda’s insistence on receipts), with little trust of underlings, suggesting far less ideological devotion than commonly believed &amp; serious principal-agent problems. Stories about terrorist incompetence are legion and the topic is now played for laughs (eg. the 2010 movie Four Lions), prompting columnists to tell us to ignore all the incompetence and continue to be afraid.<p>Also see his essay <i>Terrorism is not about Terror</i>: <a href="http:&#x2F;&#x2F;www.gwern.net&#x2F;Terrorism%20is%20not%20about%20Terror" rel="nofollow">http:&#x2F;&#x2F;www.gwern.net&#x2F;Terrorism%20is%20not%20about%20Terror</a>