Amazon's speedy one-day shipping is denting its profits

Amazon shares fell more than 6% Thursday after the company's quarterly earnings fell for the first time in two years, coming in below analysts' expectations.

Between the lines: Amazon had been posting record profits in recent quarters, but its move to offer one-day shipping to Prime customers is clearly denting the bottom line. Last quarter, the company spent nearly $10 billion on shipping, but the company has long been willing to sacrifice short-term profitability to make moves that are popular with consumers and are hard for rivals to match.

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