it has been assumed for years that the Saudi's regularly overstate their reserves of oil by some margin. The massive Ghawar filed has been pumping for decades, at some point the reserves have to be exhausted. The Saudi's though are protective of their position as the leaders of OPEC and so have long been thought keen to maintain this by saying they have the most oil.
So another Wikileaks document saying that this is suspected to be the case by US Diplomats is not really all that exciting on the face of it; except that if the US estimates of a 40% overstatement are correct then the oil prices we are seeing now of over $100 a barrel are here to stay forever, in fact a doubling from here would not be that much of a surprise.
Let's hope this estimate is just more Wikileaks stirring, if the world runs out of oil this fast then we will be cast back to the dark ages (let alone a depression too) in pretty short order. Perhaps selling off those transport stocks and topping up on oil exploration plays is a good personal hedge.