This is worth noting. CAPS II was halted two months ago so that it could get a privacy overhall. Now its back, and there has been no privacy related improvements that I can see. Whats critical is that its mission has already expanded beyond terrorism. You will now get a general warrant check for violent crimes every time you fly.

] Only a few months ago TSA officials were issuing public
] assurances that CAPPS II would remain confined to
] searching for foreign terrorists.  Now it has been
] expanded to include domestic terrorists and violent
] criminals -- all before the program is even
] officially launched.  And the definition of
] "domestic terrorist" is being steadily expanded
] far beyond the everyday meaning, potentially encompassing
] political protesters and, if recent proposals are
] accepted, even suspects in the "war on
] drugs." And how long before the system is expanded
] to search for con-artists, drug dealers, deadbeat dads,
] and so on down the scale of wrongdoing until it becomes a
] comprehensive net for enforcing even the most obscure
] rules and regulations? 

American Civil Liberties Union : The Five Problems With CAPPS II: Why the Airline Passenger Profiling Proposal Should Be Abandoned