Google removed the official Amazon app from the Google PlayStore after Amazon let slip that the app features its own hidden app store, as reported by Business Insider. App stores don't allow apps to be distributed through them if they directly replicate a function of the app store, but this ban in this case the two companies involved are in direct competition for shopping search traffic. Amazon quickly replaced the app with one called Amazon Shopping that disabled the hidden app store.
Tricky. Expect more and more Trojan schemes as everyone fights for the same customer. People are crazed.