With the massive spikes in energy prices and a constant worry about supply interruptions we have all been exposed to the theories surrounding energy supply and demand. I don't think any of us have thought of how close we are to running out. Fundamentally, the principle of peak oil (Wiki) is that we have reached the peak of world oil production and we will only have less available as we go forward.
The film The End of Suburbia examines the impact on the North American way of life after the oil age ends. Some of the stats that are used in the film are alarming. Once you start thinking about how oil and natural gas impacts every aspect of your life then you realize what would happen if it were no longer available or simply not as cheap.
I know a lot people will think that the film and the theories discussed in it are alarmist. However, if nobody is thinking about it then nothing will be done either. Start adjusting your lifestyle now to help delay the inevitable and prepare yourself for the day that it comes.