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 Pandora Media Inc (NYSE:P) dropped more than 16% Friday after the streaming music specialist turned in solid first-quarter results, but followed with disappointing second-quarter guidance.

So what: Adjusted quarterly revenue rose 54% year over year, to $180.1 million, which translated to an adjusted loss of $0.13 per share. Analysts, on average, were looking for a wider adjusted loss of $0.14 per share on sales of just $174.94 million.

For the current quarter, however, Pandora expects revenue in the range of $213 million to $218 million, with adjusted earnings per diluted share between $0.00 and $0.03. By contrast, analysts were modeling higher adjusted second-quarter earnings of $0.05 per share on sales of $219.34 million.

Now what: To be fair, Pandora also slightly raised its full-year 2014 outlook to a level roughly in line with analysts' expectations. Now, Pandora expects adjusted revenue in the range of $880 million to $900 million, with 2014 adjusted earnings per share of $0.14 to $0.18. Analysts went into the report seeing 2014 earnings and revenue on the same basis of $0.16 per share and $892.31 million, respectively. 

As it stands, the big worry is that Pandora's growth is stalling; Q1 listener hours grew just 12%, to 4.8 billion, and active listeners in March only increased 8% from the same year-ago period. This certainly doesn't mean Pandora can't reward patient shareholders as it continues striving toward sustained profitability from here; but it can only do so much over the long term as its top-line increases wane.

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.