Francisco Rodriguez:

Everyone is investing in the dollar because they believe it will hold its value. As investors flee to the dollar, the US can print more greenbacks and maintain its value precisely because of this belief. Effectively, it is paying off previous investors (who see their trust in the currency’s stability confirmed) through the willingness of new investors to buy in. This is eerily reminiscent of what Mr. Charles Ponzi did in 1903, and ever since he first tried it, it has never turned out well.