Last week, I explained How AI Conquered the US Economy, with what might be the largest infrastructure ramp-up in the last 140 years. I think it’s possible that artificial intelligence could have a transformative effect on medicine, productivity, and economic growth in the future. But long before we build superintelligence, I think we’ll have to grapple with the social costs of tens of millions of people—many of them at-risk patients and vulnerable teenagers—interacting with an engineered persona...