Stocks often drop excessively on just a little bit of bad news. Why?
If one piece of bad news gets out, investors begin to fear that more bad news is lurking around the corner. Similarly, if one stock in a sector gets into trouble (especially if it is an event that could easily happen to any other company in the same business), there is a suspicion that others, too, will suffer. For instance, investor confidence in Internet companies took a beating after March 2000, when popular Web-based companies in the U.S. faced bankruptcy.