From Paul Krugman in the NY Times

The only way speculation can have a persistent effect on oil prices, then, is if it leads to physical hoarding — an increase in private inventories of black gunk. This actually happened in the late 1970s, when the effects of disrupted Iranian supply were amplified by widespread panic stockpiling.

But it hasn’t happened this time: all through the period of the alleged bubble, inventories have remained at more or less normal levels. This tells us that the rise in oil prices isn’t the result of runaway speculation; it’s the result of fundamental factors, mainly the growing difficulty of finding oil and the rapid growth of emerging economies like China. The rise in oil prices these past few years had to happen to keep demand growth from exceeding supply growth.

I understand that is not a primary source, so take it for what it is worth. I think, however, that a lot of people are putting too much emphasis on what is essentially noise in the US inventory numbers or (worse) reading US gasoline inventories as proxies for oil inventories.

Edit: On a personal note, I made a trip last fall to visit my parents in FL. We took peak oil videos and literature with us and spent the week talking about the coming rise in oil prices. They are Fox News Republicans, and I wanted to get to them before Fox propaganda turned to peak oil.

Well, they came to visit us this week. Instead of "Gee! You sure were right about oil prices!," my father last night said, "It is all speculation. If they reign in speculation, the price of oil will be cut in half." *sigh* I think my mother gets it, but I'm afraid my father is lost to iron triangle propaganda.

I can't understand why so many people don't "get" supply & demand. Unless you can affect either supply or demand, you're not going to have a significant effect on prices. Unless there is hoarding, speculators have no effect on supply, and the only effect they have on demand is opposite to the direction of their speculation.