[nandemo]

I haven't read the book, but it just doesn't seem very plausible that one needs about the same number of practice hours to become an expert at any of several hard but unrelated skills.

This presentation goes a bit beyond that and suggests that giving presentations is like brain surgery.

The actual research articles on the subject (Ericsson and others) are really interesting, though. It's not about a magic number, but the fact that deliberate practice has a marked effect on the level of expertise.