Bruce Schneier calls this the "war on the unexpected". If you take average people, who aren't experts at security / investigating / etc, and you tell these people "if you see something, say something", then you're going to get a ridiculous amount of false positives.<p><a href="https://www.schneier.com/blog/archives/2007/11/the_war_on_the.html" rel="nofollow">https://www.schneier.com/blog/archives/2007/11/the_war_on_th...</a><p>Everything "unusual" becomes suspicious. See a guy taking photos at an airport? Must be a terrorist! Can't be a photographer and aviation enthusiast, no!<p>As Bruce says, the CYA angle is also horrific. Landlord sees something, thinks it might be nothing, but just in case, tells the local cops. Cops figure it might be nothing, but just in case, calls the FBI. Branch office figure it might be nothing, but just in case, gets regional / national HQ involved. Somewhere in the chain someone inadvertently gets word to the other 3-letter agencies, and the effect is magnified.<p>... and every time it's escalated, people figure "well, the people below me wouldn't have escalated unless they had reason to" ... while at the same time thinking, "well, I'm not sure, but I'm also not going to be the scapegoat if I fail to neutralize a potential attack and something does happen."<p>Everyone in the chain has plenty to lose and little to gain for <i>not</i> escalating to the next level -- <i>nobody</i> wants to be the guy who missed an opportunity to stop / neutralize a threat, especially in the unlikely-but-possible scenario that an attack does occur.<p>Regarding "if you see something, say something", Rick Moranis had an intelligent take on that at the beginning of his guest column in the NYTimes:<p><a href="http://www.nytimes.com/2010/05/16/opinion/16moranis.html?_r=0" rel="nofollow">http://www.nytimes.com/2010/05/16/opinion/16moranis.html?_r=...</a>