A stoppie is one of those more awesome things humans can do. It may look like a yobbo thing but the skill involved is quite something.
What's happening in that photo is what most people think happened to them when they, as a child, pulled their front brake and they went over the bars. It is not. Our friend Randy (why do the Americans just not get it?) in the photo is braced. In other words, he's balancing on his forearms as if doing a handstand push-up. He is anticipating the motion and bracing against it. What happened to @slowmotion in his youth is different. He wasn't anticipating the sudden slow-down of the bike and he didn't understand intertia as our seat-belt wearers understand it today. He wasn't braced against the slowing down, his elbows crooked and his chest went over the bars whilst the bike was still perfectly horizontal to the ground. Then his bum slid off the seat, going forward perfectly horizontal with the road. His knees then knocked the handlebars which in turn topped the bike over and he made a dive for mother earth. If he can remember, he would remember two handlebar bruises just above his knees. That's proof that his knees hit the bars. Should our friend Randy above topple over, his knees would be intact since they will not meet the bars.
That fateful morning Mrs Slowmotion Snr told her son to never touch the front brake again and since he had the fear of god in him because of that nasty incident, he obeyed. He she been a physicist she would have taught him about interntia and somehow got him to brace when braking and practiced that until it became second nature.
Unfortunately the issue is widely misunderstood and the front brake gets the blame. It is actually the best brake on the bike.
Sheldon agrees:
http://www.sheldonbrown.com/brakturn.html