I bought one of the FireTV Cubes when they were new, and goddamn, that thing is absolutely festooned with ads. And it constantly sends weird packets my firewall doesn't like, even when it's supposedly 'off', so I've ended up keeping it unplugged most of the time, just plugging it in when I want to use it.
I mean, I thought the NVidia Shields were kind of bad, with all the forced ad nonsense from Google. But the Cube is a heck of a lot worse.