An excellent article on speculation in the commodities markets from the German newspaper Spiegel:
The Attack on Prosperity: How Speculators Are Causing the Cost of Living to Skyrocket
I don't think there's any doubt there's been huge run-ups in commodities starting in August 2007 and another bump in February 2008. To my mind, this is another bubble being blown by investment bankers desperate to mitigate or avoid realizing their losses in the sub-mortgage crisis. There's clearly no willingness to shine any light onto the books of the big banks, since probably 50 % of the top ten would be insolvent if they had to truly account for the value of their highly-leveraged mortgage-based instruments of financial suicide.
Like all bubbles, this one will probably go on for longer than seems possible in spite of the clearly unsustainable nature of the beast. The investment losses, in the end, will only be that much bigger as a result. That said, I think this bubble will burst a little faster than the housing one. For one, turnover is much faster than housing. The price of commodities is rising much faster than housing did so we'll reach the tipping point that much faster.