Paul Christiano at Less Wrong:
There are many different reasons that someone could care about this technical problem.
To me the single most important reason is that without AI alignment, AI systems are reasonably likely to cause an irreversible catastrophe like human extinction. I think most people can agree that this would be bad, though there’s a lot of reasonable debate about whether it’s likely. I believe the total risk is around 10–20%, which is high enough to obsess over.
Existing AI systems aren’t yet able to take over the world, but they are misaligned in the sense that they will often do things their designers didn’t want.