What?

Google has announced that it is cutting access to Youtube on Amazon Echo show and plans to do the same for Fire TV devices soon. 

When?

As per the statement, access to Youtube on Echo show has been already been revoked. Further, coming January 1st, the access to Youtube on Fire TV will also be revoked.

Why?

Google has said, Amazon is not reciprocating the support Google provides for Amazon devices by allowing services like Youtube to run on them. Amazon had stop selling Google's Chromecast on Amazon retail website to 'avoid confusion to users'.

How did Amazon react to Google's move?

Amazon has published a statement that it is not happy with the development and 'Google is setting a disappointing precedent by selectively blocking access to public services'.