9-11 notwithstanding, are we lucky that most terrorists so far have been stupid? They either kill themselves in the act or run with no plan and get gunned down by the cops. Lots of them fail in the attempt (shoe bomber) or get easily caught in sting operations. If you declare yourself a leader of a group like Al-Qaeda or ISIL you will be hunted down by international forces and eventually wacked. Did the guy who gave the San Bernardino killers his guns think he wouldn't get caught? Not much brain power behind these acts which is probably a good thing.