Commercials, especially producers, hedge against cash positions in the physicals or against forex risk in their business or market risk in their investments, so they will always be more or less opposite the trend of price. They tend to get extreme in their net short or long positions near price peaks and troughs, so they are good at warning of reversals when they get extreme.

Speculators/funds follow the price trends and typically provide the marginal fuel for rallies/corrections. So a very interesting move is when the funds start fading rallies, like they did in copper, gold & silver, for example, in the past few months. It can signal distribution before a lasting reversal, but it can also end up marking consolidation in the market, as in silver from 9/10 to 1/11, when they began ramping up longs again. Right now they are fading silver's rise, but not sharply.

The funds have sold into Gold in a pretty big way since 9/10. I don't see any precedent in the data for such a big fade. Price has certainly not followed them yet, which shows how strong the buying has been. So it's either a huge distribution and a sharp decline is coming or they will have to come back in and that would likely drive up gold sharply.

With the US$, the funds are still following price down, but they tend to turn around ahead of the dollar (see 9/07, 9/08, 10/09, 2/10). Also, while they are at the biggest net short level since 11/07, it is not an extreme as in 8/07 & 10/07. So while the dollar can bounce here, the funds aren't signaling a big move yet.