[Edit: It turns out that all of this may take place a few months earlier, and might not actually fall that low. Probably around 1500.0 and 4000.00. But don't discount it.]
Effects the US Dollar might have if it crashes. It's a dangerous outlook but a genuine threat.
Once the Dow and S&P500 indices start to considerably recede, the confidence in the US stock market and lack of GDP growth will lead people to start selling the U.S. dollar, abandoning it as a world reserve currency and starting a domino reaction to fiat currencies all around the world.
It's coming like a huge wave in the distance and many regular and powerful folks are just relaxing on the beach building jacuzzi hot tubs and drinking beer, all the while some of their friends are screaming at them and buying helicopters. Some people just don't want to give into the fact that the beautiful and wonderful life they enjoy so much, may soon be stuck a railroad crossing with an endless train crossing by.