The End of Oil Is Closer Than You Think, page 1

I would think that the theory of Peak Oil is pretty much common sense. As our economy is built on consumption, the masses must consume in order to generate profits for the corporations like oil companies.

To increase their profits, we must consume more oil/petroleum products. I don't think that our oil supplies are unlimited, so eventually we will either run out, or be incapable of supplying enough for demand.

Just take the number of cars for example,

From link

If an alien were to land on earth, the first thing he would notice about the "green planet"is the amount of cars there are on the streets. He would see that they come in all shapes and sizes, colors and are of many different brands. He would attempts to count the cars, but would get lost quickly because no brain can comprehend a number so large. In 1900 there were only 4,192 passenger cars built in the US (the only country to be manufacturing cars). There were no buses or trucks. By 1985 there were 109 million cars in existence. Today, with dozens of countries participating in the creation of automobiles, that number is six times larger.

It is estimated that there are approximately 600 million motor vehicles being driven on the streets of earth, the alien would be dumbfounded with this number. The biggest manufacturers are Japan, producing 8,056,000 cars in 1998, the US, with 5,554,000, and Germany with 5,348,000. With passing time, these numbers experience a rapid growth. For example, in 1960 Japan produced 185,000 cars, but by the end of the 1990s it was producing nearly 10 million a year. It is believed that at this growth rate, the number of cars on earth will double within the next 30 years. In this time scientists predict that traffic congestion will become 10 times worse than it is today. If in 2001 it is difficult to cross a major street without having to wait five minutes for the traffic to stop, how long will one have to wait in 2050?

Today the alien will notice that with such a large number of cars and people on earth, there are approximately ten people per car. But what will happen when he returns for a second trip in a hundred years? Will there be as many cars as people, or maybe by that time we'll have discovered a new method of transportation that is much more efficient and eco-friendly than the car? Only time can tell.

Marina Stasenko -- 2001

Source

In the last 20 years the nuber of cars has increased sixfold! At this rate, oil will run out a lot sooner than people think.

When the oil does run out, or becomes too expensive that is when we will start to run into problems. Our whole society is based on oil consumption, so take oil out of the equation and all you have left is chaos.