[hn_throwaway_99]

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.