I believe that Mark is asking to understand yourself., and then decide on what role fits you, not what someone else tells you, or what sounds "glamorous". Art, Rajiv, Walden and Mike did what they probably felt deep inside them, but not because they became "chance" managers since someone was pushing them. You need a deep seated desire and will to push yourself to achieve it, whatever goals might be. Do you dream of being the head of a successful company, or do you desire that you invent the greatest algorithm to solve the toughest problem in this world? It may seem that the society ends up measuring you based on how many people you “command”(resource allocation, layoff-list etc!), hence the (!)logical conclusion may be to move towards management.
I believe that you must look at how many lives you can improve, and then you may be regarded as a leader. Being in a management or technical side becomes irrelevant at that point. -- my 2 cents :)