Tom Friedman, in his new book Hot, Flat, and Crowded, makes a pretty powerful argument that the US’s addiction to oil helps finance fundamentalist Islam and represses democracy. The main point: Having oil means dictators can finance repressive institutions (police etc.) and bribe the populace into apathy.
Here is a graphical telling of the same story:
Tom also says that no country with more than 50% of its income from oil is a democracy. I am not totally sure of the numbers here, but I wouldn’t call Norway undemocratic. Update, thanks to Twit from mgjosefsen: Norwegian exports of oil and natural gas was 52% of total Norwegian exports in 2005. Share of GNP was about 25 %. We seem to be an exception, in other words.