A geologist at Gulf Oil, M. King Hubbert, developed this theory in 1956: this is the point at which petroleum extraction would reach its peak and then begin to decline. He predicted that the United States, then the world's largest oil producer, would reach its maximum in 1970. This happened. As a result the seventies were a period of high volatility in oil prices. He also predicted that the rest of the world would reach peak oil around 2005. Since 2005 we also have had high volatility in oil prices, cf. summer, 2010, $4.50/gal.
Recently, Op-ed pundits and others have speculated that the United States will again become an oil exporter, having enough for its own needs, due to fracking and conservation (you don't hear that word much anymore, do you?). However, if true, this only postpones the problem of oil scarcity, it kicks the can down the road.
Perhaps today we should be thinking about mass transit, conservation, and other sources of energy.