Economists and policymakers got what they were looking for Monday: a clear uptick in the housing market. The catch is, few believe it's sustainable.

The National Association of Realtors reported that sales of existing single-family homes, townhomes and condominiums in October surged to a seasonally adjusted annual rate of 6.1 million units from 5.54 million in September -- making last month the strongest since February 2007. Sales were up 23.5 percent from last October.

Every piece of housing data is scrutinized these days because it was primarily the housing market that derailed the U.S. economy, and its recovery is key to restoring economic vitality.

Low home prices, federal programs that helped push down interest rates and a temporary $8,000 federal tax...