Based on a forum post where someone stated that advanced practitioners were more likely to get hurt than beginners:
Safety is largely a skill/mental attitude. You can go about a difficult jump with safety in mind, using spotters, progression, and building up to it - or you can just go for it. Most of us choose to go the route of safety - but sometimes someone doesn't know how to be safe. It's an inherent skill to some extent, but must be actively developed or TAUGHT (which is something all three gyms (APEX, Primal, PKV) focus on.) To address later points, these gyms don't just say "Do X and Y and never do A and B." They teach with safety in mind, and through that teaching style students learn how to be safe on their own.
However, I do think Rafe is right about the quote "Safety has got nothing to do with fitness." being incorrect. On Saturday, I took either the worst, or the second worst, bail of my life (parkour, flipping, gymnastics, martial arts, slacklining, firespinning, waterskiiing, wakeboarding all included). The only reason I am probably not paralyzed right now is because of my strength, fitness, skill, and experience.
I wasn't doing anything dangerous, just a simple step up to crane with my off leg. I stepped, leapt, my foot landed on the top, but I had a little bit too much forward momentum and I pitched forward, head first, feet in the air, toward the concrete on the other side. It was about a 4 foot drop, and all I remember is a snapshot of the concrete about 2 feet from my face, and my right arm outstretched toward the ground.
Based on the map of my (extremely minor) injuries and scrapes, I contacted the ground with the blade of my right hand and braced with the palm of my left, lowered myself down into a roll. I hit my thigh on the corner of the wall, and I must have hit my knee at some point - probably during the roll.
I ended on my back, eyes closed, on the concrete. My right leg was extended, and my left knee was bent about 45 degrees. The person I was training with came over, and I calmly asked her to extend my knee and help me unzip my jacket so I could breathe. I walked away about 2 minutes later, and now about 36 hours later the only remaining pain/tightness/soreness is in my thigh, which is greatly diminished.
I was doing something easy and simple. This was something a beginner could probably do. I am sure, however, that this was not something a beginner could have walked away from so easily. I consider myself somewhat strong, but I still do things that are largely not risky. I take great care not to put myself in any unnecessary or excessive danger. This was a technique that was not excessively dangerous. But just like any technique, if the right thing goes wrong at the perfect time...
Physical strength is JUST AS IMPORTANT as mental strength. You can not say that a beginner is exposed to less danger because it simply isn't true. You can not say that because I am stronger, I have to take more risks. Because I was stronger, I am able to move my fingers to type this right now. Life is a long road and we must be strong in order to walk it to it's destination.