I was sitting in my hairdresser's chair the other day when he said, "So I wanted to ask you something." He told me about a friend who'd lately gotten into BDSM, and who had been showing him bruises on her ass. "I don't have a problem with it but... is that really safe, to be all marked up like that?"
I get questions like this all the time. It's a perfect example of counterintuitive perceptions about BDSM. Stuff that seems heavy to the uninitiated really isn't, while activities that are casually portrayed in popular culture are actually rather hazardous.
Take bruises on the butt. People get squicked by them, but for the average healthy adult it's not dangerous to get your ass and upper thighs hit until you're heavily bruised. We're well-designed to take impact there, so if you like it, do it.
On the high-tech side, I used a surgical stapler on someone recently and it was big fun. I'm guessing many of you cringed at the phrase "surgical stapler," but in fact, it's not that intense. The staples are small and they don't penetrate the skin very deeply. So provided you employ the same common-sense precautions you'd use with any skin-piercing play, it's pretty safe to use.
Contrast this with depictions of BDSM in the media—wax play, for example. Candles seem like such common, unthreatening objects. But I recall watching Madonna pour wax on Willem Dafoe in Body of Evidence and thinking, "Hey, Material Girl, you're holding that candle very close to his bits. The wax will be quite hot, and he's likely to get second- degree burns, which are prone to infection and scarring." You can do wax play safely, but don't just pick up that colored and perfumed taper candle—average burning temperature, 145 degrees—and start giving someone a spontaneous Brazilian.
I can't count how many times I've seen people on TV hanging some or all of their body weight from their bound wrists, or tied up and then left alone. It's often presented as no big deal, but in reality, bad things can happen in that scenario. Let's start with nerve damage to your hands, resulting in permanent loss of sensation and dexterity, and proceed all the way up to death. Just ask Alabama minister Gary Aldridge—oh wait, you can't, because he's dead. He apparently put himself into some rubber bondage and then accidentally choked. Kind of a twofer on the nonsafe menu: heavy self-bondage and autoerotic asphyxia. But even having someone else strangle you during sex is a seriously bad idea. I think it seems okay to people because there's no scary-looking equipment involved, and it looks like a situation where someone could "tap out" before it was too late. That's a false impression. It is not safe. You might live through it, but every time oxygen and blood to the brain are cut off, you risk serious permanent injury or death. There's no way to eliminate that risk.
Sometimes things that seem like a bad idea are. But it's not always that simple. Listen to your instincts, but check your facts, too.