Shares of Amazon.com Inc. AMZN, -14.05% tumbled 12.5% in morning trading Friday, enough to pace the S&P 500's SPX, -3.63% losers, after the ecommerce giant reported a surprise first-quarter loss and revenue that came up a bit shy. The stock, which was trading at the lowest levels seen during regular-session hours since June 2020, was on track for the biggest one-day percentage selloff since it plunged 12.7% on Oct. 26, 2011. The stock's $360.35 price decline was wiping out $183.32 billion in market capitalization, to knock Amazon's market cap down to $1.288 trillion. The stock has dropped 24.1% year to date, while the S&P 500 has lost 10.7%.