This AP story was in the USA Today about peak oil and a couple paragraphs stood out to me:

"The least-bad scenario is a hard landing, global recession worse than the 1930s," says Kenneth Deffeyes, a Princeton University professor emeritus of geosciences. "The worst-case borrows from the Four Horsemen of the Apocalypse: war, famine, pestilence and death."

He's not kidding: Production of pesticides and fertilizers needed to sustain crop yields rely on large quantities of chemicals derived from petroleum. And Stanford University's Amos Nur says China and the United States could "slide into a military conflict" over oil.