Have a look at the chart: Over the past five years, the cost of drilling for oil and gas has crept right up to the revenue. What's going on? Well, we're getting these old fossil fuels in ever more expensive ways: deepwater drilling, tricky so-called "horizontal drilling," and hydraulic fracking. These methods are also more dangerous, as the recent mishap in the Gulf and that movie Gasland made clear.
The Oil Drum speculates that some companies may be embarking on drilling projects that won't pay off at all. As the cost of drilling keeps rising, and the return on investment keeps falling, that's going to make oil more expensive and slow down the economy. I hear there's free energy from the sun though.