Are you familiar with Primecast? A third party reversed how Amazon authenticated its movies and for a day, you could actually cast the movies that your Prime subscription allowed, including rentals. It was no different than if you authenticated on the website. Amazon quickly scrambled to shut that app down and still hasn't answered with their own method for Chromecast. It isn't even a technical issue, it is a control issue.

Now I don't know the licensing terms they have with the content providers, but they certainly aren't fulfilling the consumer demand.

No, I wasn't familiar with that. Still, the present issue seems one step worse than that.

Digital music sold used to have DRM, because it just couldn't be avoided since the licensing terms of the content required it. The Primecast seems likely to be the same.

It's more like them saying, "Sorry, user, we can't let you do that."

Where as this (and what Apple does) is more like, "What's that user? You want <competing thing>? Well, fuck off!"

Thinking on it though, massively slowing down deliveries of books from publishers Amazon doesn't like was actually the first time I've seen Amazon do something like this. So this actually isn't the first time; now its a pattern.

Side rant: Amazon Prime's media crap is also especially annoying to me personally, since I spend most of the year outside of the US, where it doesn't work at all. (Go Netflix!))