people get hurt at crossfit because they simply over train. 
if you watch the crossfit games they are hammering at their shoulders, elbows, and knees to the point where i have no doubt they will get a major injury at some point.  they also always are trying to beat PR's 
the simple solution is train smart.  a gym like this can be helpful but we tend to let ego's and peer pressure get the best of us.  this ends up getting us hurt