My wife and I like watching real-life police detective shows. Sometimes we discuss mistakes the killer made, and how we’d avoid them. “I wouldn’t kill anyone, but if I did, I wouldn’t cheap out and keep the clothes I wore to do it instead of tossing them into a river.” Of course we’re not going to do that, but it’s a puzzle to solve, so we try to solve it. We would not have those conversations around a taxi driver or a crowded subway, lest someone overhear and get the wrong idea. On an empty subway or Waymo? Yeah, sure. And if BART or my cab reported us for planning a murder, I’d be livid enough to plan how to murder the computer that made the decision to rat me out.