I'm seeing increased security line automation, with a new belt system which moves the used trays back under the in use trays, and then pops them up for loading. There signs saying to not stack the trays at the end, as there is an auto-loader that I guess looks into the first tray into the recycle bin and will stop if there is something in it. In fact I've heard TSA barkers getting quite annoyed when people stacked their own trays. Otherwise, I'm generally with the OP, just out of courtesy to my fellow pax.