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 e-commerce king Amazon.com (Nasdaq: AMZN) are plunging today, down by as much as 12% after the company reported earnings last night that fell short of expectations.

So what: Top-line revenue growth remained robust, jumping 44% to $10.9 billion, while the bottom line suffered from increased costs as net income dropped a whopping 73% to $63 million, or $0.14 per share. Analysts were looking for a tad bit more in sales but $0.24 per share in profit.

Now what: Amazon has been focusing its efforts on investing for future growth, by building up its video-streaming library available to Amazon Prime members and likely taking an upfront loss on Kindle Fire sales. The growth story remains intact, yet investors are getting shocked into selling from the big miss on the bottom line. I'm a shareholder and I'm not fazed -- I'm actually excited about where Amazon is going.

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Fool contributor Evan Niu owns shares of Amazon.com. Click here to see his holdings and a short bio. Motley Fool newsletter services have recommended buying shares of Amazon.com. 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.