One might cut Paul Krugman a bit of slack for his sorry tale of three money pits, as twice a week he faces the challenge of coming up with an economics column with some manner of hook. Unfortunately, with great prizes (and compensation) comes great responsibility, especially when an academic knowingly exploits fallacies to advance a political agenda. For its users, money has three classic functions: a medium of exchange, a unit of account, and a store of value. For its government producers, money has three other functions: a source of seignorage, a means of taxation, and a lever of macroeconomic influence. Theses various purposes can sometimes conflict, so tension arises when a monetary innovation appears that better serves some …