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 3-D printer maker The ExOne Company (NASDAQ:XONE) fell 10% today after reporting disappointing earnings.

So what: Fourth-quarter revenue fell 16% to $10.7 million and the company swung from a $900,000 profit to a $3.2 million loss. On an adjusted basis, the loss was $0.19 per share but that fell well below the penny profit that analysts expected.  

Now what: The fourth-quarter results were bad but the worst news may have been disappointing guidance. Management only expects $55 million-$60 million in revenue next year, which is below $61.6 million estimates and probably puts the $0.25 per share profit estimate in question.  

This is the danger with owning highly priced stocks like this. Shares are still trading at 10 times 2014's expected revenue, and with the loss last quarter and competition heating, up I'll gladly sit and watch this stock from the sidelines.

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.