Well, Jobs is not criticized for failing to break into enterprise software because he has had outrageously, unprecedentedly, massive success breaking into other markets. Failure is perfectly tolerable when you are good at something. Ballmer is an all around failure, and there are thousands of better candidates for his position.
I should hope to be such a failure. He served as the development manager for the original MS Windows, one of the greatest business franchises of all times. During his tenure as CEO he's taken what was already a mega-cap company and more than doubled their net income and tripled revenue.
And clearly the market seems blase - if you improve your top and bottom line and your valuation gets cut in half, that generally means investors don't think your future is all that bright.
