Since I started CrossFit, I've read and heard about the critics talk about how unsafe it is, and my only response to that is any form of exercise can be unsafe if you don't have the proper coaching, education and guidance.
CrossFit is all about constantly-varied, high-intensity movements. And to do these movements, you have to have a certified coach to take you through this - or any type of physical activity.
I have found that CrossFit has made me more fit than I have ever been.