jyms you have some very valid points. There is a real potential for beginners and others who have limitations to over do it and risk injury. Like anything else there are poor trainers in crossfit just like there are in other gyms. The key is to find a trainer who truly cares and is willing to put in the extra time to assure these issues don't turn out to be the case. A good trainer can scale any workout for any individual no matter the fitness level or physical ability.

As for the standard of the movements. There are really two different areas which need to be separated. 1st being training mode. The thought within crossfit is when training one needs to find the right balance between strict perfect form and maximum intensity. The theory being if you perform a workout as fast as you physically can yet your form is 100% correct then you've not actually performed the workout at maximum ability. Yet if you go balls out and your form is such that you are absolutely risking injury then you've gone two fast. A good analogy is one we used when I was a firearms instructor and one I've also heard Dave Castro with CrossFit HQ use. That is if you took three individuals and had them on the range. You asked them to place five rounds in the center of mass as fast as they can. All three take exactly the same amount of time. The first shooter doesn't have one round in the center of the target and as a matter of fact only has four rounds on paper and they are all over the place. The second shooter has all five rounds within about a 4" group dead center on the target. Now the third shooter has all five rounds and they are all touching dead center and really make one hole. So if we analyze the three shooters we'd say shooter one needs to slow way down. Shooter two is just about perfect and shooter three needs to push his speed even more.
Now the second area is actually competitions in crossfit. When competing they will spell out the movement standard and are very strict about how the movement is performed. As an example if performing "Fran" in a competition it will state for the thruster one must clean the weight to the racked position. Perform a front squat with the weight racked on the shoulders and the squat must be below parallel. The athlete is to come out of the squat with the weight in move the weight to a locked out over head position. Now this isn't the actual language directly from crossfit HQ I just paraphrased for the purpose of this conversation.