The basic idea of spontaneous order is quite old, as Nicholas notes, 
and it is a matter of not foreseeing the full consequences of 
actions, as Sam said. A more unique and controversial Austrian 
contribution in these matters would be the 'regression theorem' 
of  Mises, whereby money (or other such institutions) necessarily 
emerge spontaneously from self serving action.

In any case, Austrians get credit for making the case for spontaneous 
order in contemporary economics. A POW economy may come closer to 
general equilibrium than does the global economy, but that is not 
saying much, and it is more important to note that Walrasian analysis 
does not itself explain the emergence of the institutions needed for 
coordination, it just assumes that such institutions exist. It is 
more interesting, perhaps, to weigh Hobbesian or Keynesian type 
coordination failures against Ferguson or Mises-Hayek type of 
coordination success stories. Of course, Austrian Business Cycle 
theory is an example of coordination fauilure, but barring examples 
of intervention Austrian theory is in the Aritotle-Ferguson line of reasoning.

Doug Mackenzie