Folks, this defies common sense.

What does Common Sense tell you? Certain people have been through background checks, etc, and are considered Trusted Travelers.

Great, most of the time they get expedited screening and save some time. However, in no way is expedited screening GUARANTEED. The passenger does not know until the boarding pass is scanned, and then at that point in time they must go with either the expedited line or the regular line.

Why would they let someone "change their mind" upon learning the barcode in the boarding pass is "regular" and not "expedited"???

If someone had contraband in their possession and if they had been cleared for TT and if, for whatever random reason they were chosen for regular screening, they would want to catch and identify that person. My guess is that if a TT refused regular screening either by saying "I just decided not to travel today" or "I'll go back and try my luck with a new boarding pass", that passenger would be detained and thoroughly searched. I would further guess that passenger would lose TT privledges for a good long time, possibly for life.

Why do I guess that? Because during my Global Entry interview, the BCP agent stressed that if a GE passenger was ever caught with anything illegal, they would be immediately removed from GE status for life.

The GE/TT traveler has been offered an opportunity to get expedited screening and/or immigration/customs checks some, but not all, of the time. Don't like it? Don't sign up for GE/TT and do learn to love standing in long lines every time.

Personally, I'm happy with the knowledge that some of the time I will move past long lines. I have much to gain, nothing to lose, by cooperating with the program exactly.