Yeah there have been many an arguement over this at my checkpoint when a selectee gets through the checkpoint without going through selectee screening. The management simplified things by stopping TSA screeners from checking boarding passes so now there can be no arguement who missed them.
I do agree that the selectee system is largely a waste of time and needs to be seriously revamped but not all of this is squarely on the TSA. Take canceled flights as a great example, your flight is canceled and you are put on another plane a few hours later. The computer thinks you bought your ticket last minute and flags you as a selectee. In that situation the airline should de-select you but often times they don't bother.
Or I have heard stories about ticket agents getting payback on rude passengers by making them selectees.
