The terminally clueless sub-species of SLF doesn't help matters either. I picked the wrong security queue yesterday because someone about three in front of me hadn't done the business with the liquids and the plastic bag and so held up the queue while the offending items were sorted. Then the one in front of me, who'd just stood there for a few minutes and watched all this taking place, did exactly the same thing. I like to think that had that been me, I would have successfully put two and two together and achieved four, and been sorting my carry-on before reaching the front of the queue.