If Amazon the marketplace was solely responsible for the upkeep of the marketplace, they'd be more inclined to actually maintain it in a working manner. Not to mention it'd be easier for publishers to sue them to compel compliance.
Would the whole shipping network, fulfilment, and distribution centers be repeated across all of these companies or would that be a separate company? What about the vendor marketplace and ecommerce code and massive analytics systems they built? Plus customers will have to go to multiple different websites depending on what they want (babystuff.com, bookstore.com, etc)?
These companies can't simply be divided geographically and regionally like oil and telecom companies can, that's counter to how internet companies work. So it'd have to be business unit / divisional.
It's easy to throw around anti-trust laws as a panacea for all the stuff we don't like by tech companies but we seem to be missing the whole concrete picture of what that actually means in practice.
Amazon's publishing platform is only a relatively small part of their wider business and doesn't answer any of my questions.
All of these technical issues are problems of Amazon’s creation. Amazon wrote a bunch of software that doesn’t provide a supply chain that can maintain the integrity of what they sell. Sound like their problem.
Who else is responsible for the upkeep of the marketplace?
The "break them up" argument works if there is an inherent conflict of interest that would get resolved if they were separate entities, but that isn't true in this case.
The inherent conflicts of interest are everywhere. It commingles inventory, competes with its partners and encourages an auction like atmosphere for constrained product. Retail Amazon and marketplace Amazon need to be segmented for consumers to understand who and how they are buying products.