well, at least, in theory, one can cash out his deposits and keep them in the sock under the matress... it is relatively easy with Euro...

in 1991, then soviet Union, has given the pension and the pay (most people were working for government entities anyways) in 50 and 100 ruble bills, and a week later declared that the old specimens of the 50 and 100 ruble bills were being replaced with a new specimen, and each person was entitled to exchange x amount of rubles a day...
scary, what a government can do...