This currency suffers from the same major problem that all limited supply commodity-based currencies have (assuming someone doesn't figure out a way to counterfeit it) - deflation. Whether your fixed money supply is based upon gold or hard cryptographic problems, a fixed money supply encourages people to hoard money rather than invest it, because their money will be worth more later. This causes the amount of money in circulation to fall, which causes even more deflation, etc. (Google for "deflationary spiral").<p>Basically, you have 3 choices for currency. You can have debt-money (most modern economies). This has the advantage that money is effectively created by the market based upon the mutual agreement of a lender and a borrower, which means that money is created and destroyed by the invisible hand. This is a good thing. It is problematic, however, in that you get problems if large sections of the economy ever start paying off their debts through very large productivity gains because that destroys the money supply. Also, it tends to support a "banker class", who does nothing but loan money and gets paid for very little work (capital allocation isn't THAT hard compared to how much you make doing it).<p>You can have commodity money, which is great because you don't get runaway inflation. But because of deflationary spirals, you can get runaway deflation. Also, people tend to hoard whatever commodities you are using, which are typically useful for industrial or other uses.<p>You can have fiat money, but that only works if you have an incorruptible central bank. Otherwise you end up like Nigeria.<p>Personally, I think we should use the Joule as a basic unit of currency. Although energy supplies can fluctuate, they tend to grow and shrink with the economy, which prevents either inflation or deflation. Different banks could offer different baskets of energy types (wind farm or solar farm output futures, barrels of oil, coal, etc.), and you don't end up with a banker class living off of everyone else, but you don't end up with hyperinflation or deflation. 500 MJ today would tend to buy a similar amount of things 10 years from now as today (maybe a little more because of efficiency gains, but not a lot more).