The brainphone is inherently unsafe.
The brainphone disrespects the human mind by reducing thoughts to code.
The brainphone dramatically alters and pollutes the natural human body.
The brainphone violates a human’s inalienable rights by allowing corporations, governments, and online mobs to monitor one's thoughts.
The brainphone produces a hideous creature - the human/AI hybrid.
The research is vast and compelling. Smartphones and social media cause psychological, physical, and physiological damage to humans, especially young people. Smartphones and social media also tend to be highly addictive.
For all the harm smartphones cause, at least we occasionally can step away from them. With brainphones, we will be always connected. The trauma currently caused by smartphones will be powerfully amplified by implants.
The damage to humans as a species will be unparalleled. People with brainphones might find themselves living and acting as human hives, always tuned into and slave to collective thought and opinion. They might also look and behave very differently than people of today. Put bluntly, it might be the end of humanity as we know it.