[AceNZ]

There are several factors driving the value of the dollar lower:

1. Inflation. The more dollars there are in existence, the lower their value will be.
2. Low interest rates. Foreign investors, who hold a lot of dollars, are looking for the best return they can get on their holdings. As US interest rates drop, they sell dollars and buy other currencies with higher interest rates. The dollar falls as a result.
3. Demand for dollars. There's a feedback loop here too: as the dollar falls, or as the impression develops that the dollar is weak, more holders of dollars decide the currency isn't valuable or stable, and they too sell, driving the dollar down even further. (an interesting side note is the side-effects of those sales: more and more assets passing into foreign hands, higher long-term interest rates and more inflation).

The Fed caused these problems, but it's past the point now where it can cure them. They can influence only some aspects of inflation and interest rates -- there are other mechanisms at play (#3 above) that they can't control.

FWIW, I don't think we've seen anything yet. The dollar is crashing, and it's got a long way to go still. I've read some predictions of a 90% decline before it stabilises again. I've moved all of my assets out of the dollar into commodity currencies like the NZ dollar (since I live in NZ), although the AUS or CA dollars would be good too.