I'm not sure we should call it "fantastic"
The negative downsides begin at "dystopia worse than 1984 ever imagined" and get worse from there
That dystopia is far more likely in a world where the moat is so large that a single company can control all the llms.
That dystopia will come from an autocratic one party government with deeply entrenched interests in the tech oligarchy, not from really slick AI models.