It's fascinating to read up on how nations store their wealth. Around the time of WW2 a lot of Western nations got together and came up with the Bretton Woods System. It went through some machinations until Nixon took us off the gold standard. This had the effect of making the US Dollar the reserve currency for most of the world.

This has been great for the United States. We run the printing press. We can buy goods overseas with the paper we just pulled out of the copy machine. But what if we ran the presses too much? Would all those nations keep the dollar as their reserve currency? What happens to our spending power in the world when nobody wants the pieces of paper we produce?

If the flight from the dollar reaches a critical mass then the floodgates would open. Oil producing nations would drop the dollar peg and the Ponzi scheme that is the US Dollar would collapse. At least we could use green-backs to heat up our Spam.

Greenspan Tells Gulf to Drop the Dollar
Saudi Arabia buys gold (dumps dollars?)
Gold Demand Rises in Saudi Arabia
Iran said they switched reserves from dollars to gold