The S&P futures are down 12 points on news that Dubai World has defaulted on its debts, which are estimated to be $40 billion. European markets are down nearly 2%. The fear is that banks have exposure to the debt. In addition, Dubai World has assets across the globe that might need to be sold and could put pressure on asset markets.
Most thought that being long for Thanksgiving was a can't lose situation. Traders are not positioned for bad news and this could potentially get ugly as trading will be thin tomorrow. More likely the S&P will end up 12.