Clay shirky complained once that not enough women are arrogant self aggrandizing jerks. What he was referring to, was the tendency for men, and not women, to be overtly and excessively confident about their abilities - and being rewarded for it.
He's probably right. A whole host of successful people seemed to have bitten off more than they could chew, and had to fight like hell to hold on to their piece while combating those who wanted it just as badly, becoming uber-experts of the field (They were experts to begin with) once they emerged victorious.
It's arrogance in its purest form, but it's arrogance bundled with the predictive faith that the only way to understand events is to cause them. 
These people usually have a firm base beneath them. They know enough, have the right mindset, have the clarity of thought, and have the sheer stubbornness to be able to adapt on the fly and survive the impending challenges.
We shouldn't forget that it takes time to build up to that level of skill. But once it's attained, it's time to be ruthless, most harshly towards oneself (and one's ego).
 - Stolen again from Nassim Nicholas Taleb