I passed through San Ysidro with my family on a day trip to Mexico about 3 months ago. We're Anglo, I was driving a new car with California plates and we had government-issued ID for everyone in the car.

After the obligatory "what are you bringing in, what were you doing in Mexico" question the officer asked for our passports.

Now, the law changes on Jan 1 so that everyone coming across is required to have a passport, but the law wasn't in effect. I stated, quite politely, that we didn't need passports to come into the US.

Big mistake.

The officer then became extremely rude, asking all kinds of questions, having me open all my doors, rifling through our possessions, etc. We didn't have to go through secondary inspection but we were threatened with it if we gave him "any reason to look harder at us". In short, he was an unprofessional, badge-heavy jerk, and he used the law (or rather, a law not yet in force) to intimidate us. Undoubtedly this hindered him from his (ostensible) purpose of detecting illegal immigrants and terrorists.

The irrational and unnecessary TSA and Customs regulations are in place to control and intimidate the population - they are not to catch bad guys.