To get the subject back on Sale, I think that there's so man different things happening with a pitcher's motion that it's almost impossible to predict injury.
There will always be exceptions to the rule , Mark Prior is the prime example of "perfect" mechanics going wrong, and on the other side of the coin, Randy Johnson was a skinny, lanky hard throwing lefty with funky mechanics (like Sale)who went on to have one of the best careers of all time so it's honestly just a crap shoot I think.
What we do know about Sale is that he's been injury free in college and has been a rock for his team's rotation, these things both bode well for him. Aside from that we'll just wait and see.