When I flew to San Diego in January, I was pulled from line and searched, including a pat down, before I boarded the plane in San Jose. Later I learned it was because I had changed my flight reservations 24 hrs before my trip.

TSA workers in SJ aren't nearly as friendly as those in the commuter terminal at San Diego. I had quite a nice chat, including laughing about why I was pulled, while they searched my luggage (no pat down that time, just "the wand")