Funny, but *all* of my Canon EOS digital bodies will "hunt" on a still subject . . . at least in relatively poor lighting. If anything, the 1D-III is a lot better about NOT doing that.

When talk using AI SERVO shoot STILL subject, we should make something clear:

1) Is your subject is really STILL ?
2) Is you camera STILL, say on tripod ?

If one of the two is NO, then the distance between the camera and your subject is changing, plus the AI SERVO AF will kick in for sure, and with Mark III's high sensitive AF system, you will notice the lens movement more easily.

So if you shoot still subject it's better use one shot AF mode, and use AI SERVO shoot moving subject, just like Lar said that's the way how it's designed for, and of course you can shoot anyway you want, and blame the camera

When talk using AI SERVO shoot STILL subject, we should make something clear:

1) Is your subject is really STILL ?
2) Is you camera STILL, say on tripod ?

If one of the two is NO, then the distance between the camera and your subject is changing, plus the AI SERVO AF will kick in for sure, and with Mark III's high sensitive AF system, you will notice the lens movement more easily.

So if you shoot still subject it's better use one shot AF mode, and use AI SERVO shoot moving subject, just like Lar said that's the way how it's designed for, and of course you can shoot anyway you want, and blame the camera

My experience as well. But good luck getting this into the heads of others.