This is a response to David's blog about kids making bombs.
What you described is a product of the tween ego. From their early teens through young adulthood, a kids life is all about his or her ego. I'll forego analyzing a female's ego and focus on the males, since they're the ones primarily responsible for what you described.
Males want the respect of their peers. They want to be the Alpha Male. Very often, they make a direct connection between respect, and fear. They want other males, friend and enemy alike, to be afraid of them. Some achieve this simply by fighting, but most of them are in fact afraid to take that path themselves. So how do they earn the fear and respect of their peers? The "easy" way is to try and make yourself appear to be fearless, even to the point of recklessness. Or to put it simply... to make people think they're "crazy".
That's where the behavior you described comes into play. The quickest and easiest way to appear fearless, reckless, and insane, is to send the message that you get your thrills by exposing yourself to extreme danger. That you enjoy risking tremendous bodily harm, or even death. The more dangerous the stunts you perform "for kicks", the crazier you appear to your friends, and the resulting mindset inevitably is "Oh shit, don't fuck with that guy, he's fuckin crazy!".
It actually comes back to fighting. Like I said, most of them are actually afraid to get into a real fight lest they get their asses kicked, which would completely destroy their ego and ruin whatever image they had built before that. The Alpha Male NEVER loses a fight. The moment you lose a fight, you are now the winner's bitch in the eyes of all your peers. And so, as an alternative to actually fighting, they try to create the idea that hey, if they're crazy enough to do pull these incredibly dangerous stunts, then they must be absolutely fearless in a fistfight, right? If they're crazy enough to risk such severe harm to themselves, what's a kid like that got to fear from me? Surely he's not afraid of being punched. Surely he'd just shrug off anything I can dish out and proceed to destroy me. Right? Probably not, actually, but that's exactly what they want you to think when you see them doing these crazy stunts.
But why choose stunts over actual fighting? They'll only get some bumps and bruises in a fistfight, especially against other kids who are pretty much guaranteed to be complete amateurs just like them. These stunts, however, are FAR more dangerous, they could even be killed!! So then why? That's actually another easy answer. There is no chance of failure in a stunt... not true failure, as in failure to portray themselves as fearless and reckless. Even if they screw up and get hurt, even badly hurt, they still "had the balls to try it". In fact, continuing to perform the same stunts after recovering from the injury sends an even greater message of psychotic fearlessness. Yet if they lose a fight, now they're a punk-ass pussy little bitch who got pwned by so-and-so, who's obviously a superior male for having kicked his ass. That, to the tween ego, would be just about the most catastrophic thing they can experience in their social life.
Oh, they won't show a hint of fear if you try to actually fight them, they'll be all piss and vinegar, because they need to maintain the image of fearlessness. But you can bet your bottom dollar, if you either know what you're doing or if you just land a few lucky shots, you'll see the panic on their face when they realize they've gotten themselves into exactly the situation they've been trying to avoid: They're going to lose a fight. They're going to look like a little punk in front of their peers, which ironically is what virtually every last one of them actually are, but they all do everything they can to hide it and come across as a bad-ass, hard-hitting alpha male. Fearless. Reckless. Insane.