UPDATED 2:55PM: On the day its first smartphone hit the market, Amazon is smarting from a hit it took from investors. The company’s shares plunged a wince-inducing 9.7% today in the wake of Thursday’s disappointing Q2 earning report — losing about $15 billion in net worth in just a few hours. It was the worst performer on the S&P 500, which fell 9.6% today, and Amazon’s worst stock day since October 2011. Shares closed at 324.01, rebounding from an intraday low of 314.76, but continued lower in after-hours trading. UBS analyst Eric Sheridan told CNBC that investors going forward will be looking for a “continuation of growth in [Amazon’s] media business and stickiness of its Prime base.” Bank of America Merrill Lynch analyst Justin Pope said in a research note: “With growth not accelerating, Amazon could become a show-me stock.”

PREVIOUSLY July 24: Shares are down 10.2% in post market trading after the e-retailer reported a far bigger Q2 loss than investors expected. Amazon lost $126M, up from a $7M loss in the period last year, on revenues of $19.3B, +23.2%. The top line was right on target with analysts’ consensus forecast. But the loss at 27 cents a share far exceeded the 15 cent loss the Street anticipated. What’s more, Amazon warns that it could lose as much as $810M on an operating basis in Q3, up from last year’s $25M loss.

The shortfall comes from Amazon’s big investments in new products and services, including video. The company says it plans to spend $100M on original video content in the current quarter, far more than last year or in Q2. Funds also are going to build fulfillment centers, a subscription book service, the Kindle Fire TV streaming box, and its Fire smartphone.

“We continue working hard on making the Amazon customer experience better and better,” CEO Jeff Bezos says in the earnings release.