Autodidacts are often considered dangerous because they are rare and non-autodidacts consider their mode of operation threatening. Truth is an autodidact will help you more often then harm you.
Autodidacts don't cause chaos they attempt to remove it, it is the fear of the autodidact that causes the chaos.
Autodidacts should be hired, but only if you know they are an autodidact and how to handle them. This requires you to not be afraid of them and realize the benefit in having one on your staff/team.
No, it isn't some over looked animal, it means "A self taught person"
What an autodidact can do for you:
Provide a unique perspective on a problem.
Digest dry, difficult material quickly and produce results from it.
Take the time to explore new areas and invent solutions
Soak up new technologies and ideas and pool them with existing resources to generate insightful connections between what may seem to be unrelated topics.(aka thinking outside of the box)
You can learn about some autodidact experiments at: Hole-in-the-Wall