Is there excess volatility in commodity prices?

I've had a number of relatively technical posts, a couple recently, about behavior of commodity prices.  It's because I'm generally wondering if there is excess volatility in commodity prices, much like Robert Shiller and others have long pointed out about the behavior of stock prices and housing prices.

As astute readers may have noticed, I really don't have a strong opinion on this yet.  At this point I don't see any smoking-gun evidence that commodity prices display anything but rational market behavior.  But the amount of volatility we do see suggests that both supply and demand are very inelastic, and/or policies and trade restrictions facilitate what are, in effect, very inelastic supply and demand.

There is one exception.  While I haven't studied it as closely, gold prices are looking an awful lot like a bubble to me.