Gas

The national average price of regular gasoline topped $4 a gallon (3.79 liters) for the first time, AAA, the largest U.S. motoring club, reported yesterday.

"At $4 per gallon gas, $125 per barrel oil and $10 per million Btu natural gas, a lot of activity becomes uneconomical," says Mark Zandi, chief economist at Moody's Economy.com in West Chester, Pennsylvania.

The lifestyle of the exurban commuter may be one casualty.

Emerging suburbs and exurbs -- commuter towns that lie beyond cities and their traditional suburbs -- grew about 15 percent from 2000 to 2006, nearly three times as fast as the U.S. population, as Americans moved further out in search of more affordable houses or the bigger ones that are sometimes derided as McMansions.

"It was drive until you qualify" for a mortgage, says Robert Lang, director of the Metropolitan Institute at Virginia Tech in Alexandria, Virginia. "You can't do that anymore. Your cost of transportation will spike too much."

The 38-year-old Marino, an archeologist for the U.S. Fish and Wildlife Service, is among those feeling the pinch. "Eating out and discretionary income are a thing of the past for us," he says.