Notice the lowest study on the 15y weekly chart of SPX (above). It shows how far the current price is from the 4wk moving average. At today's close, the market is further away from the 4wma than it was at the worst of the 2000-2002 bear market. As Will Rahal pointed out, a regression to the mean would seem likely at this point.
No one is bullish anymore. With all the expected support levels broken (1060, etc.), it is hard not to be bearish. I think (and hope) that this will support a rally.