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 WebMD (Nasdaq: WBMD), which uses the Web to provide health information to doctors and consumers, fell more than 24% on seven times the average volume after the company lowered its full-year revenue outlook.

So what: Third-quarter revenue fell marginally compared WITH last year's Q3 and came in below expectations. Earnings exceeded by $0.07 a share, but lower guidance eliminated whatever goodwill would have come from the beat. Management now sees 2011 revenue of $555 million to $565 million, down from earlier estimates of $580 million to $600 million.

Now what: Both Carl Icahn and George Soros have taken substantial stakes in WebMD in what appears to be hopes that executives will concede to a transaction that values the business at a premium to today's levels. Management is fighting back by adopting a "poison pill" to protect against a hostile takeover. Whose approach do you believe will be best for common shareholders? Please weigh in using the comments box below.

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