That's all fine and good until the hardware, which you won't control, comes with its own prepaid cellular modem that connects at will and sends that juicy data

That's all fine and good until the hardware, which you won't control, comes with its own prepaid cellular modem that connects at will and sends that juicy data back to the mothership. Follow the consequences of your OS being effectively spyware controlled by a hostile external entity and things get dark rather quickly.