Multi focal points
It depends on the circumstance. If you have many objects in the same plane of focus, multiple focus points can trigger. The system will average out some of the subtle differences to a greater or lesser degree depending on the aperture you select. Use a high-ratio aperture and you'll find more focus points will light up and track than you might if you use a low-ratio aperture.
That said, I used 9 point mode for a long time on the 7d. When I purchased an f1.4 lens I started using the single spot-mode focus point option and get far more keepers when the object I'm photographing is close and I want to be sure the eye highlight is sharp.
In some modes, multi-point can be quite distracting. You can end up with essentially a christmas tree of red lights in the finder.
When i take shots with my 7D I generally use Single Spot focus for birding, can anyone please explain how Multi Focal points can focus on multi points. Andrew