On the bright side, smart speakers aren't even a little bit essential, so it's easy enough to just not buy them if this starts happening. I don't think the value proposition of an always-on device connected to a vast advertising network is very high to begin with. Throw in subliminal advertising and you'd have to be very... dedicated... to want such a device. If it succeeds even a little, though, they'll bake it into…
Then all ads will start with panicked screams and fire alarms.