"Finally, there is the question of what happens if other alternative digital currencies also rise. More than a dozen digital currencies are trying to compete with bitcoin. Can you imagine a world in which we all transact with dozens of different currencies every day with different rules? Neither can I."

Frankly I am surprised by Sorkins lack of research and understanding of the topic.  This quote says it all for me.  Does he not understand the current F/X market?  Different fiat systems from various central banks all manipulated for inflation, employment, trade balances etc...by governments financially, morally and ethically bankrupt.  Bitcoin or any digital currency for that matter eliminate these externalities.