Mr. Greenberg, thank you for giving George Mitchell his due. He was a great man in the truest sense of the word.
In response to FederalFarmer, it's worth noting that the prolific shale source rocks currently being tapped in North America actually underlay every petroleum producing basin in the world. Our good fortune is not due to some freak of geology, but simply a transient advantage in technology. As fracking technology disseminates throughout the rest of the world, we can reasonably expect increases in production similar to what we are experiencing at home.
We are a long, long, long way from peak oil. My guess is we'll abandon hydrocarbons for other nascent energy sources (e.g. fusion) long before we run out of oil.