I mentioned in an old post that the commercials were short the Yen, and low and behold, we got a substantial drop.
Notice, back in May the heavy short position the commercials had. Without anything fancy at all, just a basic trendline break, would have worked just fine to trade this setup. I do not use that for my trading, because I want to dial in a little tigher than that.
However, for those just beginning to study the markets, this is an absolutely valid way to trade. At the moment, there is no setup for this market. The trend is down, but the commercials are basically nuetral. If they were to go to the short side on a rally from here, that would set up a nice sell signal.