I used to work with this guy who was an electrical engineer.  He was the office GPS expert.  He knew about satellites, data transfer, ephemeris -- all the stuff an expert is supposed to know.  It was 2007, and another coworker got the brand new iPhone.  I was asking the iPhone guy how he liked it, etc., and the GPS guy said, "How does the data connection work?  Does it use minutes?"  This was in the time when you paid for a certain amount of cellular minutes each month.  Separate data connections had been around for at least a little while, and I really felt like, of all people, this GPS guy should've known better.  "Does it use minutes?"  Like, that's not even how any of it works.  It's literally two separate radios. 

I still know the GPS guy and I still think he's smart.  But damn, people have some weird blind spots.