Last week, President Barack Obama refused to allow private citizens to spend $7 billion improving America's energy infrastructure. Three years ago, he insisted that taxpayers spend more than 100 times that amount on an outlay that also addressed the nation's energy needs, among other goals. But while the Keystone XL pipeline that Mr. Obama rejected was certain to deliver a product that people want, the benefits of the president's 2009 stimulus program are harder to discern.