Amazon reported quarterly earnings Thursday that fell short of what investors expected. The company’s competitors ought to be terrified.

Typically, weak results are bad news for the company that suffers them and good news for others. That’s not the case when Amazon amzn stumbles, at least not these days. The company had a rough time making money for what seemed like forever. Now it makes sizable profits—a quarter-billion dollars in the third quarter—though on still slim margins. But Amazon still doesn’t make nearly as much as it could if it weren’t constantly investing heavily in its businesses.

The list of Amazon’s investments is long: Warehouses, leased airplanes, original movies and TV shows, its Echo voice-enabled speakers, the Amazon Web Services cloud computing business. It even is spending more on marketing.

Companies that compete against any aspect of Amazon’s interests should worry that Amazon is heading back into investment mode. That’s a really long list, and it includes UPS, FedEx, Walmart, Netflix, HBO, Warner Bros., Disney, Apple, Google, Microsoft, and IBM.

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Investors hated Amazon’s news, knocking almost 6% off of its stock price in after-hours trading. The dip reflected an unusual type of credibility problem for Amazon, which had warned investors profit growth could slow. As Nick Wingfield cleverly wrote in The New York Times, “analysts took those warnings with a Himalayan-size heap of salt.” They expected Amazon to do great anyway.

Making heavy investments is what Amazon does best. And it only sometimes cares about pleasing investors. Jeff Bezos loves nothing more than to take business away from competitors. (A favorite saying: “Your margin is my opportunity.”)

With Amazon’s profit stumble, it looks like he’s at it again.