People are looking for something that isn't necessarily going to happen. They're making the assumption that things are going to turn negative and there's no evidence to support it.
We've had a market where negative news on the economy and the corporate profit picture have dominated. Companies may have beaten lowered estimates, but we're expecting weak economic reports this week.
There's a bias, because of the bubble-popping, to be negative no matter what after we've had a good rally, because you don't want to be accused of being too optimistic.
It's really a continuation of the selling that we saw last week. Sentiment was negative going into yesterday, so a lot of people are using the strength in yesterday's prices to cut losses.
Investors, analysts, everybody that has anything to do with Wall Street is looking for the market to go down. And in that environment the sentiments becomes so negative that there is only one direction that the market can go, and that it up.