They are now, but were they at the start? I remember a PG essay where the google guys were held up as an example of how even those developers with amazing potential can still be hesitant at the beginning, unsure of whether they want to or even can run a company.

<edit>

I think this is the quote I remember...:

from http://paulgraham.com/notnot.html

"There's nothing wrong with being unsure. If you're a hacker thinking about starting a startup and hesitating before taking the leap, you're part of a grand tradition. Larry and Sergey seem to have felt the same before they started Google, and so did Jerry and Filo before they started Yahoo. In fact, I'd guess the most successful startups are the ones started by uncertain hackers rather than gung-ho business guys."