Well one example: Amazon forked Android completely, they don't answer to Google at all. In theory any OEM can do this, but most don't think its worth the effort arguably because Android is royalty-free anyway. If Google started charging even $1 per device for Android I think a lot of the big OEMs would suddenly have a change of heart.
Another example is the Nokia X for that matter, which is a pretty interesting situation.
That, and other hints, indicate that Google doesn't have much control over the platform anymore and they may have to do something about it.