"Planet Earth is finite"
Given the fact that planet Earth is finite, it follows that the oil under the Earth's surface is finite as well. The point will come, if it hasn't already, when half the world's oil will have been pumped. When this point occurs, it will become more difficult and expensive to pump the remaining oil, causing the price of oil to go up. This will signal the point of peak oil production, and each year the amount of oil produced will be less than the year before. At the same time, the demand for oil from developing countries such as China and India will be increasing. This will obviously present a serious problem for people in highly developed countries who have become dependent on huge amounts of cheap oil. The potential impact of this situation is addressed in the book "The Long Emergency" by James Howard Kunstler.