What does it mean to be a 'Key Opinion Leader' in medicine on Social Web?

What does it mean to be a ‘Key Opinion Leader’ in medicine on Social Web?

Howard Luks MD (@hjliks) asks: what is the proper role for an MD KOL?

[AS: The definition of what constitutes leadership in medicine is evolving, and I’m totally with Howard and Natasha on this. How about you?]