The markets are dealing with the following question: Is the commodity bull market spent? While there any number of good reasons for the commodity price boom there are signs that higher prices have dampened demand and unleashed market forces to seek out substitutes.

Caroline Baum at Bloomberg.com applies the "duck test" to the commodities market and finds a commodity bubble a brewing. Baum believes the manner in which commodity prices have moved, especially in light of their divergence from economic fundamentals is an indication of a bubble. A potential commodity bubble has been aided and abetted by those who have advocated investors shift a portion of their portfolios into commodities at this late date.

Nick Godt at TheStreet.com looks at whether the most recent sell-off in commodities represents the beginning of the end of the commodity cycle. While the rally may have started with good reason the question today is whether it has run too far, too fast.

"There is a genuine secular fundamental story," says Anirvan Banerji, research director at the Economic Cycle Research Institute and a contributor to RealMoney, TheStreet.com's sister site. "But commodities, and industrial commodities in particular, are cyclical by nature, which literally means that a downturn is inevitable. There's no insight on whether that's tomorrow, a year from now or later."

Michael Kahn at Barron's has a technical look at the gold and silver markets and finds them overextended and showing divergences.

On the flipside, Warren Buffett's Berkshire Hathaway (BRKa) disclosed a significant new stake in ConocoPhillips (COP).

Also, Jeff Matthews has a piece up on the trend towards the "re-nationalization" of fossil fueld reserves.

Speaking of bubbles we noted some contrarian thoughts on the potential for an ethanol bubble. Now more indications that the ethanol boom is a bit extended.

John Ketzenberger in the Indianapolis Star reports on the "absolute gold rush" that is the ethanol boom. There are plans to build up to thirteen ethanol plants in the state of Indiana. This increase in ethanol demand for corn will have a downside in the form of higher corn and general food prices.

AutoblogGreen notes a report that Chevron (CVX) is exploring the idea of building their own ethanol plant(s) to help ensure a steady supply of the alternative fuel.

Lest you think everything has changed, Autoblog reports that Texas may soon be raising the speed limits on their interstates to 80 mph. While it may represent a bow to reality it is probably not the best message to be sending to drivers at this point in time.