This thought occurred to me after having recently viewed some YouTube videos. A number of these videos I've seen have involved two siblings (brothers, sisters, what have you) engaging in a friendly TUG, only to be interrupted by an overly concerned parent. The parent usually proceeds to scold the kids or put a stop to the game altogether.
I can say that mine seemed on the fence about it until one particular time. My older brother tied me up in our bedroom, turned out the lights, and shut the door. I was about 8 at the time, so when he didn't come back I got worried and started yelling for him. My dad hears the commotion and enters to see me tied up on the floor. He cuts me loose, looks at the both of us, and flatly says "no more tying each other up".
It's definitely not the worst reaction, but after that day we ceased all of our TUG activity. Perhaps if they had humored us, while also stressing safety and perhaps setting some ground rules, then we could have continued on.
So, how did your parents react? Did they write it off as "boys being boys", or did they think it was just a phase? Did anybody's parents actively encourage them or take part? I'm curious because so far all the parents I've seen have actively tried to stamp out that sort of behavior.