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: Nokia (NYSE: NOK) dropped 17% in intraday trading today after the company hung up on prior guidance and lowered expectations for the remainder of 2011.

So what: For the current quarter, Nokia expects revenue "substantially below" its prior forecast of 6.1 billion to 6.6 billion euros, and operating margin could be near breakeven, rather than its prior forecast of 6% to 9%. Management said that "visibility is very limited," previous forecasts for the third and fourth quarters and full year are "no longer valid," and it's "no longer appropriate" to give full-year targets for 2011.

Now what: Management blamed competitive dynamics and market trends across multiple price categories, a product mix shift to lower-priced, lower-margin products, and pricing tactics by Nokia and certain competitors. The company also acknowledged that transitioning its phones from its proprietary operating system to Microsoft's Windows operating system was creating strategic challenges. Meanwhile, Nokia's comments about competitive dynamics, market trends, and pricing tactics by certain competitors could be an ominous sign for other industry players.

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Fool contributor Cindy Johnson owns shares of Microsoft. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.