One of the interesting challenges I have encountered in the past when dealing with leaders at various levels in corporations is the phenomenon of the leader whose knowledge is deficient in a key area, but who publicly (at least) refuses to recognize this. Quite often the leader rises to high office without addressing the deficiency. Logically, you would think that they would (a) realize that they lack knowledge or skills in this area, and (b) hire somebody to focus on it. In reality, most of the time, they do not try (b). However, more bafflingly, they often appear to fail on (a).
One example is a software company that I worked for in the UK. It had been founded by a software consultant and he built the company up to 75 employees in the UK and 75 in the USA. However, soon after I joined, he lost the leader who held together the consulting group of the company, and who had been instrumental in persuading me to join. The guy quit and went to work elsewhere. The founder's comment to another employee who pointed out that the guy was an excellent people manager was revealing. He commented "I really don't know why we need a man-manager. Everybody should be able to manage themselves".
In the case of this entrepreneur, his comment was a symptom of a wider feature of his worldview, namely, that everybody else would be much better off if they behaved exactly like him. However, the basic problem remained, namely that he lacked an appreciation of empathetic, people-centered leadership. Ultimately it contributed to his inability to grow the business, and led to his eventual departure, since in the meantime he had sold the business to a US corporation who expected profitable, continuous growth.
More recently, I worked for EDS during the end of the Dick Brown era. Dick was a deal-maker, he had no real interest in operations and execution. He got excited about the next big sale or deal. As a result, execution processes (starting with this pesky little thing known as due diligence) were neglected during his period as CEO. The inability of the corporation to execute on poorly-structured and optimistic deals signed by him was a major contributor to a crash of the stock price, and his credibility declined thereafter to the point that he was forced to resign. Once again, a leader was undone by his failure to provide any focus on areas that he himself had little interest in.
As a positive example of how you should manage, one can point to Microsoft during the period where Bill Gates was the CEO and Steve Ballmer was the COO. Gates' visionary ideas, unbalanced by his awkwardness in public, lack of interpersonal skills or interest in minutae were balanced by Ballmer's ebullient, street-fighter personality and focus on operational details and execution. Gates was smart enough to realize what he was not going to be any good at, and in Ballmer he found a personality to perfectly complement his own.
Over the years I have come to characterize people with this leadership deficit by the summary "they often don't know what they don't know, but if even they do know they assume it is unimportant, and therefore can safely be ignored". Needless to say, it is frustrating to deal with such people, since every time you try to draw them into a discussion of the "black area", they lose interest and then it is hard to avoid them shutting you down. I even invented a phrase to summarize this behaviour pattern when applied to software developers, many of whom labour under the dangerous delusion that they are qualified to design a user interface, when in fact they would be downright dangerous in any form of Human-Computer interaction design role.
It turns out that my purely anecdotal observations are also paralleled by academic observation and research. The pathology is part of a wider pathology where people become convinced that they are good at something even when even the most favorably-disposed observer can see that the reverse is true.
Specifically, David Dunning and Justin Kruger conducted research after Dunning wondered whether it was possible to measure one’s self-assessed level of competence against something a little more objective — say, actual competence. He and Kruger published a paper, “Unskilled and Unaware of It: How Difficulties of Recognizing One’s Own Incompetence Lead to Inflated Self-assessments,” in 1999.
This multi-part article in the New York Times blog discusses the research and the phenomenon in more details.

Dunning and Kruger argued in their paper, “When people are incompetent in the strategies they adopt to achieve success and satisfaction, they suffer a dual burden: Not only do they reach erroneous conclusions and make unfortunate choices, but their incompetence robs them of the ability to realize it. Instead they are left with the erroneous impression they are doing just fine.”
It became known as the Dunning-Kruger Effect — our incompetence masks our ability to recognize our incompetence.

This could perhaps be the origin of the old saying "ignorance is bliss"...
The article on the New York Times blog is actually a long article about the wider phenomenon of anosognosia - the inability of people with body deficits such as paralysis to even recognize that they have the deficit. To an outsider it looks like a particularly extreme case of denial, which of course it is. The last part of the article contains a nice Venn diagram summarizing the extremes of self-delusion into which we can all fall, with denial in the center.