I just bought a google home (it's only just been released here), and if it either plays me adverts, or other adverts (ab)use it - I will return it to the store without hesitation. This was not sold as an ad-supported service.
To take an extreme position - Google should take Burger King to court via the computer fraud and abuse act - they've just performed a distributed denial of service attack on google's servers by using thousands of peoples google devices simultaneously without their permission.
Also - this is a key reason why google need to spend some time on supporting custom hot words for google home. 'OK google' and 'Alexa' are the audio equivalent of IoT devices with a default 'username:admin, password:password' on your network.