Great British Pound did when it lost its status as reserve currency

So we cannot expect the Fed to solve the weak dollar issue, because they are the creators of it! The Fed could start aggressively raising interest rates and we could see the dollar soar to new highs. But there is a low chance of that happening, as they have indicated the contrary. As the credit crisis unravels, we can expect the Fed to continue cutting rates. With a weak stock market, a weak real estate market, and a weak economy, we can expect more doom and gloom before we see the light at the end of the tunnel, and in the meantime the US Dollar can sink another 80% or more, as the Great British Pound did when it lost its status as reserve currency.

Technically, once a downward spiral starts in currency, it is very difficult to stop. In stocks, an issuer can buy back shares in order to dry up liquidity and stabilize the price; a common practice among penny stocks listed on pink sheets. However if the US Dollar declines, the Fed would need Euros in order to buy back US Dollars, and since the Fed is not an issuer of Euros, it would take a near act of God to convince the ECB to loan the trillions necessary to support the dollar in the event of a default or run on the banks. While the Fed does have some mechanisms in place to stabilize the markets, the act of supporting your own currency is like pulling yourself out of a sinkhole by your own hair. Once the selling starts, it could feed on itself and create a downward spiral as the value goes down more large holders, worried about further losses, may panic and sell, thus adding fuel to the fire.