1. In the big picture, totally random. In the smaller picture, it appears to be in hubs/gateways. Hubs are a difficult place to assert your power to leave, in that a large percentage of people aren't at home, or at their destination, and can't exactly just walk. If you see gate-searches for SFO-JFK, not many people are going to just say "forget it, I'll just drive".

2. The TSA's position regarding administrative searches appears to be "submit or leave", yet all of the publicity I've seen surrounding this is at the CP, not inside the sterile area. If someone stood their ground politely and firmly, I'd presume they'd have no legal recourse to do anything (unless refusing an administrative search is probable-cause or reasonable-suspicion to do an LE search, detainment, or arrest). Yet polite/civil doesn't get into the news (and no, I'm not advocating violent public disobedience, just making an observation!), and that's what brings this debate to the public forum. And there's always that $11k civil fine they can dangle over your head.

Interesting to see (at least) two threads on the same day talking about administrative searches inside the sterile area. The searches are going up, the awareness is going up, or both?