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 data storage equipment specialist NetApp (Nasdaq: NTAP) sank 11% on Thursday after its quarterly revenue and guidance disappointed Wall Street.

So what: NetApp's second-quarter earnings managed to top estimates, but a miss on the top line -- $1.55 billion versus the consensus of $1.55 billion -- seems to be triggering fears of an even bigger than expected drop in demand. In fact, the shares are flirting with a new 52-week low and are down roughly 40% in 2011.

Now what: Management now sees third-quarter EPS of $0.56-$0.60 on revenue of $1.52-$1.61 billion, while Wall Street had been forecasting EPS of $0.63 on revenue of $1.65 billion. "In general we go through periods of good news followed by bad news," Chairman and CEO Tom Georgens said. "I can't say we're on a steady trajectory up." Of course, as long as investors are willing to put up with choppy demand and, in turn, a volatile stock price, NetApp's PEG ratio of less than one -- now in line with that of rivals EMC (NYSE: EMC) and Hewlett-Packard (NYSE: HPQ) -- might be worth pouncing on.   

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This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.