Energy price forecasts that seemed to be on a prolonged rampant upswing have taken one heck of a U-turn. Take Goldman Sachs (NYSE:GS), for instance.

As recently as May, the company noted an expectation that global crude prices could reach $150 to $200 over a 6- to 24-month period. By last month, the firm had "settled" on a $110 average price for next year. But now, with prices having dropped by a whopping 50% just since July, it's cut its forecast for the year-end U.S. crude price to $70, down from its previous expectation of $115. Beyond that, it says that the $50 level is possible should the current credit and financial crises continue.

If that series of prognostications strikes you a little like driving by looking in the rearview mirror, you may have a point. But from my perspective, it flies in the face of predictions from energy seers like ExxonMobil (NYSE:XOM) and the Energy Information Administration arm of the Department of Energy, both of which expect energy demand to increase by between 40% and 50% by 2030.

Admittedly, lots can happen between 2009 and 2030 (including a special price-cutting OPEC meeting next month), but it's also inescapable that we're still paying today for the crude price declines in the 1980s, which resulted in a severe reduction in infrastructure spending and a decline in the numbers of students studying petroleum engineering, geology, and other energy-related curricula.

And while lower crude prices and more reasonable gasoline prices at the pump may please you -- and they should -- keep in mind that a too-severe decline in energy levels could have dire consequences down the road:

  • As the major importer of crude into the U.S., Canada’s oil sands development could be hindered. 
  • Development of energy assets in places like Russia and Kasakhstan could be curtailed.
  • Development of the big new discoveries offshore Brazil likely could be slowed.
  • Work on alternative energy forms could be marginalized, putting us in the soup as the world's thirst for energy ramps up.

These trends -- along with the precipitous declines in energy shares during the past few weeks -- signal a tremendous (and renewed) opportunity for investors in the energy sector. I'm inclined to point to the likes of Devon (NYSE:DVN), Halliburton (NYSE:HAL), Weatherford (NYSE:WFT), and Diamond Offshore (NYSE:DO) as names that should register prominently on Fools' watch lists.

Of the energy names mentioned above, Devon, Weatherford, and Diamond Offshore all sport a full five stars as awarded by Motley Fool CAPS members. Do those rankings include your votes?

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Fool contributor David Lee Smith doesn't own shares in any of the companies mentioned. He does welcome your questions, comments, or criticisms. The Fool has a disclosure policy.