> However, in the event this were ever actually tested they might as well have defaulted since the resulting inflation would be so high that currency would be worthless. Going from "can't get your money out of the bank" to "your money can't buy anything" isn't exactly an improvement.

While I could see this being true, I don't see how pulling cash from my bank and storing it under a mattress helps this scenario at all. Inflation hurts every dollar equally, regardless of whether it's stored in my bank, under my mattress, or is sent to me from the FDIC.