In Japan, an investigation into Livedoor -- hardly a premier Internet company -- was a convenient excuse to whack the Nikkei 225 stock index down 462.08. If breaking 10,000 will make traders nervous, below 9000 the fear levels will be palpable. At that point, any one of our laundry list of negative catalysts might come into play. In my war-gamed scenarios , the dollar doesn't have to go into crisis, and the avian pandemic need not kill millions; instead, the investing public need only become alarmed that something nasty might occur to take fear levels up toward panic. The move from Dow 8800 to 6800 won't be a rational, calmly contemplated affair. No one will be quietly wondering about option-expensing or multiple compression. Instead, it will be a severe overreaction to some external event. If and when that happens, it likely will be the best buying opportunity in the markets since the October 2002 cyclical lows.