Today's Wall Street Journal has an important front-page article on why oil is at an all-time (non-inflation-adjusted) high even though inventories are at an eight-year high. It's well worth a read.
The short answer is that refining capacity hasn't kept up, and that federal policies are a large part of the problem. Drilling is banned in an important part of Alaska, banned off the Virginia shore even though Virginia seems to want drilling, and banned so far off Florida's shoreline that Floridians themselves should be embarrassed by the amount of ridiculous deference shown to them. And regulations of all sorts have made new refineries for 30 years a losing proposition -- and until last year's largely execrable Energy Bill, which at least had a few good provisions in it, nuclear power was similarly burdened and therefore far too little used. Then, of course, there's this: "Even as crude stockpiles have swelled, U.S. inventories of gasoline have fallen as refiners have shut down operations to perform maintenance and prepare to meet new government-mandated fuel formulas...."