Oil runs out before an economically viable replacement is devised, leading to global chaos. All the major systems that depend on oil, including manufacturing, trade, transportation, agriculture, and the financial markets that serve them, will begin to destabilize. The boundaries between politics, economics, and collective paranoia will dissolve.
Markets fail worldwide, resulting in economic collapse: mass unemployment, rioting, famine, and death. Countries begin to fight again each other and eventually start the use of weapons of massive destruction.