I recently read Robert Bryce's recent book, "Gusher of Lies," in which he describes one of the pitfalls of increased energy efficiency: more consumption.
Bryce refers to a 2004 report from the National Commission on Energy Policy which posits that even if CAFE standards were increased to 44 mpg (2007 standards were only 27.5 mpg), America's fuel consumption would sill increase by 3.7 million barrels per day by 2025.
The basic argument is summed up as he quotes authors Peter Huber and Mark Mills: "efficiency fails to curb demand because it lets more people do more, and do it faster-and more/more/faster invariably swamps all efficiency gains." (Peter W. Huber and Mark P. Wills, The Bottomless Well: The Twilight of Fuel, the Virtue of Waste, and Why We Will Never Run Out of Energy (New York: Basic Books, 2005), p. 109)
This seems like a compelling argument for more focus on conservation, as described in Dr. Webber's "Conservation Can be America's Oil Weapon" article, rather than efficiency gains, although both are important pieces of the pie.