It's no secret that America's sprawling, car-dependent exurbs were Ground Zero for the economic meltdown. These "drive 'til you qualify" communities were built on risky decisions and over-leveraged debt—buyers betting that the price of gasoline for commuting wouldn't go up too much, or that they'd be able to sell their pricey McMansions before their artificially low mortgages reset. Millions of homeowners lost that bet, and the entire world paid the economic price.
But we haven't gotten rid of the danger. In fact, the worst might be yet to come. Energy costs continue to skyrocket, making travel and heating exorbitant. New research suggests sprawl is hurting our health. For example, rates of obesity in unwalkable suburbs are near epidemic levels. And local municipalities that tried to grow their tax base through sprawl may soon be overwhelmed by the extra costs of maintenance.