Gresham's law only applies when free market currencies are not allowed to compete with fiat (by decree) currency.
Otherwise, Thier's law applies, and works in reverse.
from
http://en.wikipedia.org/wiki/Gresham%27s_law#Reverse_of_Gresham.27s_Law_.28Thiers.27_Law.29These examples show that, in the absence of effective legal tender laws, Gresham's Law works in reverse. If given the choice of what money to accept, people will transact with money they believe to be of highest long-term value. However, if not given the choice, and required to accept all money, good and bad, they will tend to keep the money of greater perceived value in their possession, and pass on the bad money to someone else. In short, in the absence of legal tender laws, the seller will not accept anything but money of certain value (good money), while the existence of legal tender laws will cause the buyer to offer only money with the lowest commodity value (bad money) as the creditor must accept such money at face value.
So, this time instead of gold, we will have Bitcoin (which will be hoarded as per Gresham's law), and all kinds of "paper" derivatives inevitably entering the circulation as a means of exchange. These "papers" allegedly backed up by Bitcoin will in fact leave behind them only inflation, even despite Bitcoin intrinsic deflationary nature...
And welcome back to fiat!