Gresham etc.

Gresham's law is for when people are required to accept the 'bad' and 'good' money equally; then people will hoard the good money and transact exclusively in bad. When the coercive requirement is not satisfied, one ought to expect good money to drive out bad, or else they will float related to the risk, ease of acquiring it, etc. See http://en.wikipedia.org/wiki/Gresham%27s_law#Reverse_of_Gresham.27s_Law_.28Thiers.27_Law.29

(And if people are worried about the euro, they can hold other currencies like the deflating yen; if they are worried about dollars, they can hold euros etc)