Leadership VS Management

t seems all you hear in conversations about problems with organizations is leadership or a lack thereof. When we study management the following are almost universally acknowledged as the four core functions:  Planing, Organizing, Leading, Controlling.  It amazes me that even today Leadership is considered a function of management.  Do you agree or disagree with this?  Is leadership simply a function of management?  Or, should leadership be it's own discipline equally as or more important than management?  Can one be both a good manager and a good leader?  What is your opinion?  Briefly discuss one or all of these points in 500 words.