I like to think in terms of the energy wasted by all the bank employees driving to work every day. If even 10% of those made redundant by a distributed banking system were able to start working from home doing other things, I'd guess it was a net win.
Actually, what I said (or implied) is: fire most bank employees, all of whom will end up doing something more useful, and 10% of whom will no longer need to drive to work every day. :)
