The Golden Mean

In Book II of the Nicomachean Ethics, Aristotle discusses the Golden Mean, the mid-ground between deficiency and excess. For example, in social intercourse, the mean is wit, the deficiency boorishness, and the excess buffoonery. He believes virtue to be in-between the two extremes, and by living the mean we will become virtuous and good people. He admits that acting as the mean suggests is incredibly difficult, and it is easy to slip from the mean into excess or deficiency, since sometimes they are closely related. The question that must follow is whether the mean is always the good thing, or whether excess or deficiency is at times necessary or good. Is the mean the right thing to act upon, or does it breed mediocrity?