This is very close to the way ours work
http://www.youtube.com/watch?v=CQHu3t-0QEA

Of the three nuts in question, the bottom most adjusts the bearings. The middle (called a lock or jam) nut locks the bottom nut in place, and the top most nut holds the yoke in place. The top most nut does nothing to adjust bearings. The bottom and middle nuts are hidden from view when triple tree is fully assembled.

If someone did indeed try to adjust the steering bearings by over tightening the top most nut, then a concerted effort should be made to keep this person away from all tools, vehicles of any sort, and other assorted sharp and pointy objects.