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 online restaurant reservation service OpenTable (Nasdaq: OPEN) plunged 16% on Wednesday after its quarterly results and outlook disappointed Wall Street.

So what: OpenTable's first-quarter profit managed to top estimates, but a small top-line miss -- $39.4 million versus the consensus of $39.6 million -- coupled with a disappointing full-year outlook is forcing investors to lower their growth estimates yet again. Weakness in its international business -- due in part to the slow integration of U.K.-based rival TopTable -- is weighing heavily on results in particular, triggering serious concerns over its long-term prospects.  

Now what: Management now sees full-year revenue of $158 million-$164 million -- well below Wall Street's view of $168.2 million -- and expects its international business to record a loss. "We're focusing our efforts in areas that we believe position the business to realize the long-term opportunity in both our North America and International segments," reassured President and CEO Matt Roberts. Unfortunately, with a still-lofty P/E of roughly 40, I'd wait for much bigger pullback before buying into that bullishness. 

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