Not planking, but equally stupid. Back in the early 70's a couple of young missionaries were temple-hopping. One decided to mount a statue while the other took a photo. This being the 70's, they took the film to a developer. When the shop owner developed the photo, he sent it to one of the newspapers. All hell broke loose....the two were sent to jail for a year....freed after 6 months by the mercy of the King.
http://en.wikipedia.org/wiki/Missionary_(LDS_Church)#Incidents
At the time of the incident, I remember thinking what would be the reaction if some visiting Asian (or today, Muslim, God forbid), sauntered into St Patrick's Cathedral, and for the sake of a souveneir, asked his mate to take a photo while he mounted the shoulders of Christ on the cross. Sounds incredibly stupid, but then it's obvious that sometimes people do incredibly stupid things.
I've seen young Thais mounted vertically on the seat of a motorcycle racing down Tanon Tahahn late at night. The only good thing I can see about doing this is, you won't be injured if you crash.