What is meant by backing here? In order to backup a currency in my meaning of the word, a currency backed by "x" means you can use the currency, reliably, to buy "x". Backing with gold when you don't have gold is meaningless. Backing with energy when you don't have energy, likewise. I've made a theoretical proposal that if the government nationalized geothermal energy, developed it and then had a supply of it, you could have an energy-backed national currency. It won't be done and probably a good thing since to be benign we would have to have national governments that acted in the public interest. Transition to such a type of governance is problematical. So now we have a currency theoretically backed by the government's ability to tax its citizens and require those taxes be paid in its currency. In the midst of astonishing levels of government debt and needs to create more one of the few things our presidential candidates agree on is the need to cut taxes. True, McCain would cut taxes on the rich and Obama on the poor, but cutting taxes is not disputed. McCain's strategy has a current difficulty. A great many people who were expecting to get rich soon (or sometime) are now beginning to worry just a bit about becoming poor. Losing your house, your job, your health insurance can do that to you. Even if it just happens to a friend or a brother-in-law, it can concentrate the mind as they say.