Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of MEMC Electronic Materials (NYSE: WFR), whose silicon wafers are used in a variety of chips for computing and solar technology, fell more than 13% in early trading on roughly three times average volume after lowering its earnings forecast for the full year.

So what: Third-quarter revenue came in well ahead of estimates at $859 million. Even so, management expects just $2.7 billion to $3 billion in sales for the full year. Analysts had forecasted $3.4 billion, according to data compiled by Yahoo! Finance.

Now what: Why should you care? The same oversupply issues that threaten the likes of LDK Solar (NYSE: LDK), Suntech Power (NYSE: STP), and Yingli Green Energy (NYSE: YGE) appear to be having a real impact of MEMC. Beware buying in on weakness, Fool. Do you agree? Would you buy shares of MEMC Electronic Materials at current prices? Please weigh in using the comments box below.

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