Chromecast is a feature that you develop on your own apps - i.e. Amazon can add it to their Prime App. Google isn't preventing Amazon Prime from having Chromecast support.

This is some pretty high level misinformation. Amazon (or anyone) can write apps against the Cast API (https://developers.google.com/cast/). Amazon has just chosen not to.

Yeah I don't get it either. It doesn't impact consumer's ability to get either product.

Would we force Ford dealerships to sell Hondas as well? For Whole Foods to carry Safeway-branded products?

Of course not.

Your car dealership analogy doesn’t hold any water. Amazon is an “open” marketplace with millions of products, some of which are amazon private label and compete against other third party sellers on Amazon. Amazons track record with this is ugly http://fortune.com/2016/04/20/amazon-copies-merchants/

This is more akin to a scenario if apple were to block Spotify from the App Store because apple provides a competing service to theirs, totally leveraging and abusing their power to diminish competition. It’s hard to argue that not allowing them to sell the physical product on amazon isn’t anti-competitive, regardless if amazon does or doesn’t develop chrome cast capabilities into fire sticks.

This is laughable - >> Both the Apple TV and Chromecast were pulled from Amazon in late 2015. The company’s justification for the move was that consumers would be confused and frustrated if they purchased streaming devices that didn’t offer a direct, convenient way to view Amazon Prime Video content https://www.theverge.com/circuitbreaker/2017/12/14/16777508/...

How is Amazon any more an "open" marketplace compared to a grocery store? Because it's online?

I would say so, they are not limited to a certain amount of shelf space or square footage like grocery stores are. On average, grocery stores work much more intimately with their vendors than amazon works with theirs (or did, now that they’re breaking into the grocery business).

I was mainly thinking of how an unlimited number of third parties can essentially sell whatever they please on Amazon, unless of course you’re google or apple selling a competing product that doesn’t help amazon achieve their goals for an ancillary service that has nothing to do with their online marketplace. I can’t think of a good analogy to a grocery store scenario.

Amazon calls itself "The Everything Store" and has enough market share that it is legally reasonable to think about if it is a deal facto monopoly governed by antitrust law

Monopoly? There is nothing stopping other companies from selling the same things Amazon does.

Any what is Amazon's share of all retail sales? My understanding it's in the single digit percentages.

Amazon had 4% of US retail sales in 2017, although that's 44% of US online retail sales. Online sales were 9% of retail sales.

Apple policy is in fact to block aps that compete with iOS standard apps, unless the are so popular that apple is forced to concede

Can you point to anything in particular? I can't find any examples of them doing this recently. I saw something from 2008 but since then they have likely realized they would open themselves up to anticompetitive claims if they continued.