I thought that the original study was just showing a correlation. That is, that experts typically had 10,000 hours of practice into their field of expertise. People have claimed causation since then (i.e., 10,000 hours guarantees expertise). The weaker claim that 10,000 hours of practice is necessary (but not sufficient) in order to become an expert seems reasonable to me.
Thanks, yes, that's the other important point: you can't turn it around and expect a guarantee of success. I believe the original study didn't even claim any magical threshold of hours either - Gladwell probably just introduced that as a literary device: "10000 hours", and the added suggestion of some mystical threshold, make for much better storytelling than "oh you know, on the order of tens of thousands of hours" :)
And then if you add the other caveat too, it becomes too underwhelming to make for inspiring bedtime reading: "on the order of tens of thousands of hours, provided that you were quite great to begin with"!
Yes, too underwhelming to catch on as much as Gladwell's interpretation has. However, it actually makes an important point: even if you're talented, it requires practice to really become an expert.
