Computer Viruses.
'Nuff said.
If it was safe, useful and cheap then I’d strongly consider it. But I don’t expect that for decades, especially not in this regulatory environment. Right now I wouldn’t trust it to not be used to spam me 24/7 with advertisements or be used to monitor me. And if the wrong people take over you can expect it to be a combination “loyalty” implant and torture instrument.
Basically, I expect to be long dead of old age before the technology, regulations and politics reaches a position where I’d go for it.