It's less Google Play and more breaking the control Google has over the Android platform, despite Android being open-source and spread out across a number of manufacturers. Google Play is a critical piece of that control.

The ads look like a way to defray that cost.

I wonder what Samsung will try to do. Something similar or something from out of their own playbook?

Partner with Amazon? I know when I got a Galaxy S4 the OEM Android included the Amazon App and Google Play stores. While they may do something different in Korea, it seems like a reasonable move in markets where Amazon has traction.

Does Amazon actually provide compelling apps on their store? The comments here and this new advertising platform would suggest otherwise.

Amazon's app store is a cesspit, full of either very similarly named Apps to ones on the play store, but that do something different, or people just straight up stealing other people's Apps and selling them themselves.