Look at seat belts. Initially, they were just there, and you didn't have to use them. Then, what, around 1986 or so, they became mandatory, but not the type of offense for which a police officer could pull you over. Today, you don't even have that, even if you are Ma Kettle, living in the middle of nowhere, and use your car just to go to the grocery store.
I know that's a lame analogy, but my thinking is that the trusted traveler program would be too tempting a program not to impose it on everyone who flies, after it becomes so popular with a flying public which detests the lines and searches, as Spiff and others do. It makes the government, by extension, popular in turn.
Look at another example of where the government takes a "temporary" program and makes it permanent: toll booths. None of them were supposed to last, it was only until this was paid for, or that was paid for, but the money was just too good, so they broke their promises. Now, they have EZ Pass, which can make toll booths obsolete, and give us back our freedom to drive without them, but you are still paying the toll tax!
Edit: as I look at this post, I know I could do better, but I'm kind of tired - sorry!
[This message has been edited by anonplz (edited 01-23-2003).]