AlphaGo won twice against Lee Sedol, one of the greatest Go players in history. This is a significant milestone in the history of AI, because the sheer scale of the problem space Go has is one of the biggest among the games humans play.

This makes me think hard about how and what to teach our future generation to prepare for the era when people will blindly follow many decisions that have been made by AI without (or incapable of) fully comprehending their meaning and consequences.