What makes exercises dangerous?

I've received a lot of criticism for stating that certain exercises are bad or dangerous. I've repeatedly say that I think that the weighted deadlift isn't a good exercise. I've come down harshly on some kettlebell exercises too. I hear people talk about things that could go wrong with even bodyweight exercises that could make them potentially dangerous too.

Let's just state the obvious: Any exercise can be dangerous. If you slip and lose the proper form when performing any exercise, if you do an exercise that is too advanced for you, or if you go too fast and lose control then you could injure yourself. Every physical endevour carries a risk of injury. So, what makes one safer than another?

In my not-humble, non-expert opinion, there are a few factors. One that comes to mind with the weighted deadlift is how close the exercise puts your lower back to a posture that could injure you (flexion of the lower back). If the back rounds even a little, then you could be walking away with a sore, injured back. The lower back muscles are made for extension, not flexion. When they flex, they get hurt! I'm not alone in my assesment on this one. Mike Boyle, a strength trainer for pro athletes, doesn't have his professional clients use the deadlift.

Other factors that come into play are exercises that create muscular imbalance. An exercise that overdevelops certain muscles create muscle imbalances that also lead to injury far too easily. The bench press is a prime example of this one. Granted someone could balance out the lack of serratus anterior and rhomboid work in the bench press with exercises such as the face pull but let me ask you this: why not just do pushups? That way the chest muscles get evenly build without doing two exercises. Plus, you don't need any gear to get the job done.

These are some of the reasons why I label some exercises bad or unsafe. They cross the line of risk vs. pay-off. Still, I'm not an expert and believe it or not I'm not trying to tell you what to do. If you want to do weighted deadlifts or bench presses, then do what you want. You don't need my permission or blessing. I'm just a guy making observations and suggestions. Just be careful, no matter what you do.