Diffusion of responsibility?
When trying to create something disruptive and radical, it is much easier to screw things up than to get them right. (There are more Dunning-Kruger poster children with grandiose over-estimates of their own ability out there than there are actual geniuses.)
Most corporations are structured to restrain loose cannons in positions of authority, because everybody except the loose cannon in question is afraid of losing their meal ticket. (See, for example, the recent fiasco at HP, where Leo Apotheker decided to turn HP into a fundamentally different kind of corporation and did immense damage to internal groups that didn't fit within his vision.)
The standard form of corporate restraining structure is the committee. Committees are designed to promote consensus decisions, and consensus decisions stop random-looking outbursts from happening. From the stake-holders' point of view, this is a good thing. However, committee decision-making gets in the way not only of the very common bad internal entrepreneur, but in the way of the much rarer good internal entrepreneur.
The last time Steve Jobs answered to a committee was 1985. And they fired him. Thereafter, he carefully structured his working environments as start-ups, where the founder could impose their autocratic will on the company without having to drag a boat anchor of committees after him. For most people, this would have been disastrous. Luckily for Jobs, he was as good as he thought he was.