So many people (Gladwell, Cohen, and apparently the Brazen Careerist person) have referenced this 10,000 hours claim, but no one has cited the actual research paper that came up with this notion. The paper actually addresses almost all of his points.[1]
"There are more high school swimmers than ever, therefore more opportunities to find and train great swimmers. They have access to diet, training, technology, and facilities that didn't exist years ago. That's all." Yes! That's the point! The authors of the research point out that "the fastest time for the marathon in the 1896 Olympic Games was just a minute faster than the required entry time in ... races such as the Boston Marathon," _because_ people now know the proper way to focus their efforts at practice.[2] 'Practice,' here, being training and diet. But it still takes 10 years or so of _deliberate practice_ to become world class. It's just that the bar for world class has been moved.
"I'm a case in point: I practiced the piano for an hour a day for more than ten years. I became good, but there were others who practiced twice as much who were worse, and still others who practiced less and are much better." Again, he is unwittingly supporting the 10,000 hours claim. The study points out that "the view that merely engaging in a sufficient amount of practice, regardless of the structure of that practice leads to maximal performance has a long and contested history."[3] It is not just 'putting in the hours' that matters (because then one falls into the trap of assembly-line-worker syndrome, where "improvement of performance was often arrested at less than maximal levels"), but rather what it calls "deliberate practice," which takes quite a bit of very hard work and practice tasks that are defined in a very specific way. (There's a good description of the characteristics of deliberate practice on p. 367 of the study). That is, people who just practice for hours without much thought as to what that practice should be and how it will challenge them in new ways are doomed to be less successful than those who are coached through a process of deliberate practice. It's quality, not quantity.
All that being said, I don't think being an entrepreneur actually has anything to do with being an expert. It's much more luck and hard work. Cohen gets around to saying this too. I agree with him. I'm just not sure why he felt the need to try to refute the current literature on becoming a domain expert to say, "Hey, becoming a domain expert probably isn't your goal. Your goal is to become an innovative entrepreneur."
[1] http://projects.ict.usc.edu/itw/gel/EricssonDeliberatePracti...
[2] Ibid, p.366
[3] Ibid, p.365
--> Edit 1: matrix cited a more recent text by the same author I was describing: http://news.ycombinator.com/item?id=1142983
--> Edit 2: Oops. The Harvard Business Review article that Penelope Trunk talks about was actually written by the same person who wrote the paper that I cited and the book that matrix referenced, so my "but no one has cited the actual research" claim was inaccurate: http://www.coachingmanagement.nl/The%20Making%20of%20an%20Ex...