IT'S BUSH'S FAULT!!
Sorry... I had to get that out of my system.
There is more supply than demand. Speculators expected another disastrous hurricane season to hurt US and Mexican production. This would have driven the price up and handed the speculators a nice profit. The opposite has happened and over production (in anticipation of a falloff in oil from the Gulf of Mexico) is driving the price down. The speculators are now jumping ship and making the price drop even further. Making matter worse still is that OPEC can't stop its members from cheating; they need the cash.
Well, I for one is glad Rove has turned his hurricane machine off for now, I am leaving for a month in Arizona on monday