Cooperation is no longer enough at these "suspicionless" checkpoints where everybody is treated with suspicion. Here a driver who answered 17/18 questions and provided a driver's license, military ID, and two passports was detained for 34 minutes and had his boss called during the encounter and weeks later had a letter sent from the Border Patrol to his boss.
Cooperation isn't even enough anymore.
http://www.youtube.com/watch?v=5SBEdk9FyGw