According to a recent Washington Post article, "If every one of the 70 million acres on which corn was grown in 2006 was used for ethanol, the amount produced would displace only 12 percent of the U.S. gasoline market. Moreover, the "new" (non-fossil) energy gained would be very small -- just 2.4 percent of the market. Car tune-ups and proper tire air pressure would save more energy."
The biofuel argument is certainly timely and popular, but like many solutions, it does not come without its own set of problems.
One might argue that biofuel production is our latest bandaid solution to an issue that needs to be more deeply examined: our energy usage. Perhaps rather than using cheaper fuel, we need to also use less fuel.