Prices go up, demand goes down, supply goes up, prices go down:

Mild winter weather has something to do with it. So does heavy selling by financial funds. But a largely overlooked factor in the recent plunge in oil prices may portend an end to the multiyear rise in crude: For the first time in years, the developed world is burning less of it.
...
Other signals, both economic and psychological, have been popping up for some time: Demand for gas-guzzling sport-utility vehicles has been falling, while investment in and sales of alternative fuels such as ethanol are booming. Even the Bush administration is vowing to reduce America's dependence on crude.

Sometimes I'm so smart I scare myself:

OPEC seems to have forgotten the lesson it was taught in the late 70s and early 80s: the US may piss and moan about high oil prices, but if they stay high enough long enough we will change our consumption habits, and that will have a profound, very long term effect on oil prices.

Yeah, put that in your "government is the answer" pipe and smoke it.