Leaving aside the dangers of extreme levels of AI for the moment, the problem posed by the upcoming automation revolution is a bit more complex than most describe it.
In theory, it's an economic bonanza: much less human effort will be needed to supply essential (and many non-essential) human, material wants. The problem is what it does to our system of distributing the nation's wealth among its citizens: the job system. In the past, technological revolutions destroyed many jobs, but replaced them with new jobs. However, the new jobs tended to be in industries and fields that were just as necessary as the those the old jobs had been in. The horse groomer and buggy driver became the car driver.
But in the coming tech revolution, many, many jobs may be destroyed, far down the chain of human needs. That means that the jobs and work product that remain might in fields like caring for the elderly, baby sitting, childcare, and other such things. People will have time on their hands, so we could find them productive work to do. But that kind of work, while valuable, won't necessarily be seen as something that people truly need. Thus, there would be a temptation to simply hoard the savings that will result from an automation-induced drop in the costs of most material items and the kinds of services that can be automated with AI. These savings would, in theory, make all of us much richer. And then we could all have much nicer, human-oriented jobs with reduced hours. But if people don't feel inclined to pay for the products of such work--if people decide they'd rather look after their own kids more, skip massages, and avoid classes at the community center and just pocket the cash, or buy even more cheap material goods--then we have a Keynesian aggregate demand problem. We just won't be able to make the money flow the way it needs to.
If that turns out to be the case, then we may need to either modify the classic employment system or introduce something like a guaranteed minimum income to properly distribute the nation's bounty among all its citizens. You really don't want just a small group of 21st Century robber barons who own all the robots and AI programs--all the real capital--and have trillions of dollars, while the rest suffer.