To all the abused 7D focus issue owners

Zone focus will work for tracking a moving target in AI-Servo mode as lomg as the background isn't too cluttered or busy. It's pretty awful (IMHO) for more general purpose use for much the same reason that all-points doesn't work well. You're asking the camera to decide on what your intended subject is in what ends up being a fairly large area. If your subject is isolated and/or close to the camera and contrasty, it might work, however if there is any confusion as to what you're trying to focus on within the zone, the camera may well pick the wrong target and you'll end up with a back or front focused image. Frankly, I never use it. I prefer single point (nearest the subject) for ststic subjects and expansion for moving ones with spot focus enabled occasionally for small targets.