In my personal experience what slows it all down the most is the actual people flying. Every time I fly I see countless people wearing tons of metal/jewelry/belts/whatever that they have to take off, often not till they are told to do so, the laptap is tucked far away until last moment. They still carry all sorts of lotions and liquids on for some unknown reason. When they then exit the scan they clog up the line by…
Um, excuse me? If I've just been made to disassemble my person and be less secure, you can damn well bet I am going to take my time reassembling myself and making sure I have everything back in its rightful place before proceeding. I'd recommend everybody do the same, even if that means holding your ground if the goons start trying to assault you into moving forward.