SAN FRANCISCO — Writers are peeved at Amazon. On Thursday, investors became disgruntled too.

The company, which is embroiled in a very public conflict with the publisher Hachette, announced second-quarter losses nearly double what Wall Street predicted. It also warned that the third quarter would be worse. Much worse.

That was enough to make the stock plummet in after-hours trading. Shares quickly fell 10 percent, shaving more than $15 billion in value from the high-flying retailer.

Amazon long ago proved that it could sell vast quantities of goods to tens of millions of people, and that it could simultaneously develop new businesses while innovating with old ones.

What is a more debatable question is when — or even if — all those investments will truly pay off.

“Skepticism is increasing,” said Colin Gillis of BGC Partners. “It’s hard to have $20 billion in revenue and not make any money. It’s a real feat.”