Many different players and causes.
Oil is sought in places where it costs more to extract.
There are threats to oil supplies from many sources. For example, Iran threatens to blockade the Straits of Hormuz.
Threats of war increase the prices of oil futures as many buyers try to lock in prices. It is ironic that many on the right attack Obama about oil prices but are willing to attack Iran, a major producer of oil.
Although U. S. demand for gasoline is the lowest in some time, world-wide demand is increasing. Oil and gasoline are traded on world markets, not local markets.
And finally, many U.S. refineries are closing down because they can't be cost effective because of the types of oil they use are in short supply. See "Angry About High Gas Prices? Blame Shuttered Oil Refineries", Matthew Philips, Business Week, 2012-02-24.
