As I wrote below, the bear case going forward is based on negative fundamentals - subprime housing problems and slower economic growth. In contrast, the the bull case is almost purely technical, essentially arguing the market isn't cheap but not overly expensive right now. Up until now, bullish traders have also had strong technical reasons to stay glued to their charts irrespective of fundamental news. Now those charts are showing bearishness and possible technical reversals. I think it's going to be hard for them to maintain their bullishness going forward. In addition, I think they will pay more attention to bearish news going forward.
Food for thought.