Earnings. As the unprecedented housing boom gave rise to economic bravado and unabashed consumer spending, with banks willing to finance anything levered to real estate, and with consumers literally using their homes as ATMs to finance autos, boats, landscaping & pools, college tuition, home entertainment theaters, etc., the stores were packed, home improvement stores were buzzing, people were buying RVs, new autos every year, and 44 foot Searays en masse. Now, with the incredible fall in the value of residential properties, so much so that 1/2 of homeowners are underwater and the remainder who have any mortgage exposure would be lucky if they have net equity (albeit with the banks unwilling to extend equity lending re anything tied to such homes), and with the steep and rising unemployment crisis gripping the global economy (not just the U.S.), and with banks tapped out - unable and/or unwilling to extend consumer/business financing, look for an even further drop off in the level of consumer and business spending in years going forward. Equity markets are about to catch an even worse case of cholera than they've already experienced. Earnings (lack thereof) will cause them to throw up so much that they'll dehydrate themselves. Businesses will continue to lay workers off, people will continue to be either fearful of being laid off or actually laid off, those with or without money will refuse to spend money on all but the most basic of goods, and this vicious negative feedback loop is set to keep repeating itself. Some people think Dow 5000 is unlikely. It may be much more likely than anyone wants to admit.