Another interesting article by Nick Szabo is here: http://unenumerated.blogspot.com/2006/02/irreducible-complex..., where he discusses proof-of-work (2006) and what he saw as the problem with it.

Actually, a compelling theory is that Nick Szabo (possibly in collaboration with others) is Satoshi Nakamoto: http://likeinamirror.wordpress.com/2013/12/01/satoshi-nakamo....