[actuator]

I personally think Amazon's dominance in ecommerce of physical good is fragile and it would be hard to argue monopolistic behaviour there. If Shopify grows like it is growing right now, it would be quite easy for brands to build their own stores through it without bothering to list on Amazon. At least the ones with their own name pull can afford to do this.

[treis]

Amazon hasn't really been able to use their dominance in online retail to any great extent. They failed or are after thoughts in every other market they entered. Video, music, phones, tablets, auctions, handmade (i.e. etsy competition) and their app store are the ones I can think of off the top of my head. Profit margins aren't great either.

The only really abusive thing that they do is around eBooks. They definitely have a monopoly there and doing anti-competitive things to maintain it.

[panopticon]

Their AmazonBasics line has been very successful and incredibly anti-competitive too.

Before you go and compare it to brick and mortar in-house brands like Walmart has, consider that Walmart has a higher investment in things they end up stocking in store (they pay for things up-front and shelf space is comparatively scarce). Amazon doesn't have the concept of "shelf space", and Amazon doesn't paid for the product up-front in many cases.

Walmart is notoriously pushy on suppliers, but once product is on the shelf both Walmart and the supplier's interests are heavily aligned. Amazon would rather peddle you their Basics line instead.

[actuator]

Walmart's interest are only aligned till they can cut a better deal with some other brand or they come up with their own product.

[panopticon]

I didn't ascribe any virtue to Walmart's position, but it helps to illustrate how Amazon is able to be much more effective at corning the market.