Hmm... Wait a minute. If a central authority like the U.S. government issued the coins AND run the transaction servers as a public serve then they could use digital signatures even for the nodes in the network with an ordinary distributed hash table implentation. They could issue a bunch of 10 cent, $1, $10, $100, ... and so on coins. Very efficiently and to a small public service cost. The wallets can be digitally signed with a national ID system (a potential Orwellian danger perhaps but anyway) and that would eliminate the need for messy cold storage with paper wallets and all that cumbersome management. That's something for Obama to look into.