Much as the term bellwether indicates a marker of future trends, a bellwether stock is one that is roundly believed to predict market trends. Bellwether stocks are, typically, the top company (or companies) in a specific sector that predict the industry's future health; an oft-cited example is Microsoft (MSFT), which saw its shares drop by approximately 11 percent Friday.

Of course, in the context of the recession, it's harder to pin down what's a bellwether stock and what's not. Many online financial glossaries point to General Motors (GMGMQ) as a bellwether stock; one site refers to GM as "one classic example of a bellwether stock." So what does it mean when a bellwether goes in and out of bankruptcy, is propped up by the U.S. government, and has shares that are usually deemed worthless?

The relevance of bellwether stock predictions took on particular importance this week, when the Dow Industrials average jumped above 9,000, a remarkable rebound. While this figure, the highest since January, seems just cause for optimism, the bellwether stocks' performance amid this market boost has been troubling. As TBM's "Today's Business Press" pointed out on Friday, key predictive companies like Microsoft, American Express (AXP), and Amazon (AMZN) aren't playing along. If we place our trust in the bellwethers, excitement would seem a bit premature.