In reply to john arran: I am not sure if it was in Outlier or not, but I read somewhere about the people who score highest in IQ tests often fail to succeed. I am pretty sure it was a Gladwell book, so he did go onto cover those who fail to a certain extent. I have to agree that Gladwell does have some flaws, if you compare arguments between Gladwell and some of the same topics covered in the Freakonmics series they differ quite a bit in their conclusions.
Similarly it was Ericsson a scientist/researcher who developed the theory, Gladwell just made an effort to add colour to this simple idea by introducing people who fitted that concept and telling their story. Ericsson came to his conclusions by interviewing a lot of people considered experts in their feild and came up with the 10000 hours as a rough guideline, as what stood them apart from their peers. There are of course other things that the 10000 rule simply overlooks.
Ericsson also suggested that the practice has to be deliberate and cover the three points I made above for it to hold true in a generalised sense. Simply going to the wall for 10000 hours won't make you an expert climber, unless you focus on deliberate practice. What I take away from that is even if you do engage in deliberate practice for 10000 indoors, then you will be ever be an expert at climbing indoors, as it is quite specific.
For anyone wanting an introduction to Gladwell, some of his stuff is online. He wrote a nice article on choking and panic.
http://www.gladwell.com/2000/2000_08_21_a_choking.html