My understanding used to be that it's OK if one company has a natural monopoly, but it's not ok to leverage that monopoly to gain an unfair competitive advantage in a different area. That was the rationale for the antitrust suits against Microsoft in the 90s: being the natural OS monopoly was OK, but they couldn't leverage that position to be the natural browser monopoly, too (which they did anyway, but whether the sanctions against them worked is a separate topic).

So, I would think the same would apply here: it's ok that Amazon has won a monopoly as a retail channel, but starting to leverage that to sell their own goods should be against antitrust laws. However, it seems that in the last 2 decades the only thing that courts have considered is "is the price lower for the consumer", so most antitrust laws appear to have been eviscerated in any case.

That seems a bit all or nothing. It could be worth considering if someone has monopolistic power (or some oligopoly) in one area such as distribution of products, any product business must be run separately via Chinese walls or just not allowed.

People seem to forget a fundamental part of capitalism is that government should intervene to maintain a level playing field. Then...what defines a level playing field..

That's fair, but Amazon has only a small % of total retail sales (4% in 2017, according to a quick search). I'm not sure at what point it's commonly assumed that a company has monopoly or market power, but I'm pretty confident it's not 4% or even close to that.

edit: another quick googling says that US courts apparently almost never conclude a company has market power if they have less than 50% market share: https://www.repository.law.indiana.edu/cgi/viewcontent.cgi?r...

Amazon is still growing at a good clip but I'd be really surprised if they were able to pass even 20%, let alone 50%.

Or forty-four percent of online sales. https://www.cnbc.com/2018/01/03/amazon-grabbed-4-percent-of-...

I'm not sure that's a super meaningful distinction for market power. It's a different method of selling, but ultimately you're selling largely the same things. You probably wouldn't separate out "Ford has this much market share in dealerships vs online sales" most of the time, for example.

Well, I suppose that's the key question. But I think that yuo might argue it is, because there's a huge "long tail" of goods that you can only really hope to sell online.

It is. Monopolies only exist within context. Zero to one has a good section on this.