If you didn't catch it, read my intro post below. There's also some links in there to primers, etc.
This post, however, will be an attempt to sum up a pretty complex topic.
Hubbert's Peak is reached when demand for oil exceeds production and supply.
Let's be clear, peak oil is not about running out of oil. However, there is a finite amount of oil in the earth. At some point, we will have taken half of it. That is Hubbert's Peak.
So, peak oil is about the end of cheap oil. Cheap oil has bred a lifestyle of convenience and excess, especially in America that is going to be difficult to maintain once the supply begins to shrink and will perhaps worsen the already growing class divide that exists in the United States.
The less oil there is available, the more expensive and treasured it will be. Competition, if not war, over resources is likely.
Combine this idea with increasing demand from modernizing countries like China and India, and you have the recipe for disaster. I am reminded of a quote:
"A third of humanity doesn't want to ride bikes anymore; that has profound geopolitical implications."
--Anne Korin, the co-director of the Institute for the Analysis of Global Security (May 1, 2005)