Nothing nearly as nefarious as the couple of examples above, though I can certainly understand the reasoning.

Meeting up for vacation for our families, my friend emailed me their itinerary with PNR. To help him realize that lots of mischief can ensue from including your PNR on an itinerary, I changed his meal on an international flight to a restrictive religious vegetarian meal. His wife and kids thought it hilarious too. All in all, a cheap and funny lesson learned.