Amazon has quietly hidden a Google Play Store app they had released in September which included integration with Instant Video and their own Appstore. In turn they have released another app dedicated exclusively to shopping for physical goods. A change in Google's Developer Distribution Agreement is what has caused the shuffle, according to a statement from Amazon. You can still find the old Amazon app through a direct link, but it won't turn up on searches. For now, Instant Video and the Appstore are available when installing Amazon's app over your browser.
Presumably the change is due to a noncompete clause in the developer agreement. We've seen the Humble Bundle, another popular distribution platform for digital goods, recently removed from the Google Play Store, potentially for similar reasons.
Obviously Google can do whatever they want on their platform. One can hardly blame them for protecting their market, but would you guys consider it a better use experience being able to access alternative digital stores without having to download apps outside of the Play Store? Does it ultimately make a difference either way?