The most viable argument I've heard for it is the difficulty in providing all possible constraints to narrow the path of optimization (so as to accommodate human norms). I.e. Facebooks negotiating bot developing their own language.
And for people saying it's not an issue for the next decade, I don't get this argument. Saying this is not the equivalent of saying it's not dangerous at all. In fact, the same could be said for global warming, could it not?
Plz enlighten me