Peter Beinart wrote a solid article in Time an issue or two ago regarding the falling of freedom around the world. He makes a solid point about the price of oil and level of personal freedom:

Then there's oil. As Thomas Friedman has noted, the price of crude and the tide of freedom tend to move in opposite directions. Before 9/11, the price per bbl. fluctuated between $20 and $30. Now it hovers between $50 and $65. And that's not likely to change anytime soon, given rising demand from China and India. That gives oil-producing autocracies such as Russia, Iran, Venezuela, Sudan and now Nigeria more money to crush or buy off internal dissent. And it makes it easier for them to win friends and influence people around the world. A decade ago, authoritarian governments were largely on the defensive. Today Venezuela's Hugo Chávez is cloning himself in Bolivia and Ecuador. And Iran is on the verge of dominating the Middle East.

Easterly made a similar point in "White Man's Burden":

A natural resource oligarchy is particularly inimical to democracy. Oil is infamious for undermining or preventing democracy. Oil revenues are very easy to redistribute, so wealthy and well-connected insiders who benefit from oil controlled by dictatorship have a lot to lose from a democracy that would surely result in redistribution (as I noted in a post last year). Hense, we get oil societies desperate to prevent democracy, ranging from the oil-rich Middle East to Africa. NYU politics professor Leonard Wantchekon documented systemactically the association of resource wealth with autocracy in Africa, as others did using worldwide patterns. Wantchenkon shows that new democracies have succeeded in Africa mainly in resource-poor places such as Benin, Madagascar, and Mali, while oil-rich states such as Algeria, Cameroon, Gabon, and Libya still have dictators. Worldwise, oil producers were on average in the worst fourth of the world's countries in democracy in 2004, as democracy was measured by three World Bank researchers. (125-126)

Just today, the Wall Street Journal reported on the state takeover of the one of the last independent news sources in Venezuela, and the impending distaster awaiting that country. Their quote, "Having built his claim to legitimacy on the spurious assertion that he presides over a democracy, you can bet that Mr. Chávez would not have gone after RCTV unless he deemed control of TV news vital to his survival. It may indeed be. The reason is because the economy has been so mismanaged that a crisis now appears unavoidable. How it will end, in rationing and hunger or hyperinflationary madness, is hard to say. But when the whole thing comes a cropper, the last thing the president will want is TV images of popular protests that could be contagious." Seems to fit the studies presented above.