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.

Steve Symington has no position in any stocks mentioned. The Motley Fool recommends Pandora Media. The Motley Fool owns shares of Pandora Media. Try any of our Foolish newsletter services free for 30 days. 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.