I think the most viable criticism is the lack of elasticity in a supply. Jeff Snider has articulated this well on a number of occasions. While, I think the keynesian consensus that money supply needs to be elastic is generally a farce, I can see the argument why during a time of crisis such as after a natural disaster the ability to expand the money supply helps expedite the relief and rebuilding efforts. I think this can be overcome through credit issuance, cooperation and charity but it is definitely an interesting thought experiment.