All RB/RZ users should be familiar with the random "What kind of movie are you shooting?" passerby. I can't count how many times that's happened. Of course, a smile and a short, down to earth explanation usually helps. Showing people the viewfinder is also quite rewarding, for those who have never gazed directly upon a ground glass.
Am I the only one who has had to explain the ground glass and repeat that no, it is not electronic and does not use batteries? (Yaschiamat in my case.)