Are they innovating an investing in a way that's good for consumers in the long run or just their shareholders?
I think Amazon has been a net good for consumers, in that they tend to provide quality products and services at fair prices, and overall the existence of Amazon has probably improved more lives than it has hurt.
But the sheer size and scope of Amazon's business has gotten scary, and presents a real danger. So far, Amazon has mostly used their size to benefit consumers rather than to exploit them. But the way Amazon treats their competitors, their retail suppliers, and even their own employees in their distribution centers should serve as a warning. On the surface, Amazon is a trusted and well-liked brand. Behind the scenes, they're ruthless and relentless.
First Amazon dominated the online bookselling business. Then they drove retail booksellers out of business. Then they dominated all online retail sales. Then they dominated cloud services. They're now seeking to dominate streaming video, music, groceries, smart home devices, logistics, healthcare, and more.
That's a lot of power for one company to have. And the more power Amazon amasses in one of these areas, the harder it is to compete with them in the others, because they can pour endless amounts of money into ventures that aren't yet profitable whereas smaller competitors can't.