Here is a crazy theory: Say you have a really big oil field. Really really big. Unimaginally huge wealth flows in every day because the world wants, nay needs this modern lifeblood. How do you store that wealth. Do you stack IOU's from those countries in the form of currency? Nah. They will just inflate the currency to pay you back after they burn up all that precious oil? How about you just meter out enough oil to meet your life needs? Nah, they'll call your country a terrorist axis of evil and invade to help the oil flow.

ok how about this. How about you do a deal and pump as much oil as possible as long as you can exchange it for something real. and you have a long time cultural affilation for a yellow shiny metal. yeah that will do. How about we do a deal. We keep the oil pumping as long as we can exchange a ratio of oil barrels for this shiny metal. When the oil runs out in a hundred years or so we will have a stack of shiny metal to trade back.

More reading at this blog: http://fofoa.blogspot.com.au/2009/08/call-of-century.html