I was arguing to a friend recently that I found it persuasive that the high price of oil must be due in part to some market manipulation. When I looked at the behavior of consumers--U.S. drivers have cut their mileage by 30 billion miles since a similar period last year--I felt that the demand was not very elastic. People seem to be willing to change their usage due to prices, which should relieve some of the supply/demand pressure.
Yet prices continue to rise. But wait, Paul Krugman makes some strong arguments that speculation isn't to blame. His most persuasive angle is to point out that dramatic price inflation exists in markets where speculation isn't technically possible. I'm not sure I'm sold--for instance, I don't know what the supply looks like in these other markets--but it's an article that gives us conspiracy folks pause.