Recently, Amazon released a new version of their app on Google Play Store with their own app store built in it. Since September 9, 2014 that this update has been for download on the Play Store, but it was removed on December 11, 2014.
TechCrunch reached out to Amazon about this subject and the answer was:
We launched a new Amazon App for Android Phones on September 9 that provides an award-winning mobile shopping experience, enables customers to discover and purchase all of Amazon’s digital catalog, and provides customers access to the Prime Instant Video player and unlimited streaming of over 40,000 movies and TV episodes. Google subsequently changed their Developer Distribution Agreement on September 25. As a result, we removed the app from Google Play and published the Amazon Shopping app. Customers who want the best Amazon experience on their Android phone, including access to Prime Instant Video and Amazon’s entire digital catalog, can still get the Amazon App for Android Phones at amazon.com/androidapp.
This Amazon app broke Google’s policie and it was available for download via direct link. But on the Play Store it’s still another Amazon app, the Amazon Shopping app. This is the same application but it doesn’t have the Amazon App Store built in it.