>I suppose my preconception was that the camera would switch focus >areas if the subject that was under, say, FA#1, moved to FA#2.
The camera can do that if you are using something other than single-point, like dynamic group and dynamic area. You first need to get the focus lock using the center of your chosen group. Then the camera will use the adjacent points to assist with the tracking. However, you need to do your part in trying to keep the subject under the point you chose in the start.
The more points involved with the tracking, the slower the camera is at the tracking. Whether you notice the difference will depend on your abilities and your subject.
---------+---------+---------+---------+---------+ Joseph K Seattle, WA, USA