Taibbi lays it out pretty clearly.
Wikileaks: Speculators Helped Cause Oil Bubble | Rolling Stone Politics | Taibblog | Matt Taibbi on Politics and the Economy
The issue here, which I covered somewhat in Griftopia and in "The Great American Bubble Machine," revolves around the influx of speculative money into the commodities markets. Because of various changes to the way commodities were traded -- including a series of semi-secret exemptions handed out to commodities speculators, allowing companies like Goldman Sachs to popularize commodities speculation -- there was, by the summer of 2008, a cascade of investor money pouring into commodities, mostly all betting on a rise of commodity prices. Much of this might have been due to money flowing out of mortgages and into the "safe" haven of commodities, with exploding energy prices being an unwelcome side effect. While there was less than $20 billion of speculative activity in commodities in the early 2000s, by 2008 that number had jumped up to well over $200 billion, with virtually all that money being "long" money, i.e. bets on a rise in prices. All of that new money turned into a battering ram pushing prices through the roof. We are seeing the same phenomenon this year.
The Wiki documents show that the Saudis had long ago concluded that this increased investor flow was a threat to disrupt the markets. An embassy cable from 2007 recounted a meeting U.S. officials had with Yasser Mufti, an Aramco planner. "The Saudi analysts indicated a link between higher oil prices and the influx of investor funds into the oil markets," it read.
The cables also show that the Saudis urged the Americans to enact reforms to rein in Wall Street, calling for speculative limits and other changes. It also showed that some Saudi officials believed that speculation added as much as $40 to the oil price during the height of the bubble.
All of this is significant because both the Bush administration and the Obama administration have denied this narrative to various degrees. The CFTC only recently admitted that speculation played a role in the 2008 mess, having originally (and stubbornly) blamed supply and demand issues. Subsequent analyses have shown that the Saudi position, that worldwide demand for oil never increased nearly enough to account for the gigantic 2008 price spike, was almost certainly correct.