Canon's face detection system

[BMG]

In the process of documentary/news photography I had had to following and photoraphy people who ccome out of a building and walk directly to a waiting vehicle. I was wondering if anyone in the situation have used the face detection system to keep focus on the person walking? I almost never use this feature unless I am recording video when the individual is walking. Knowing that too many faces could be an issue I was just wondering if anyone has tried this?

[shadowsports]

This is going to depend on several factors.  Motion, lighting, the lens, and number of people.  A camera with face detection will do a pretty good job in most situations, but it is possible to fool it if you have a large number of people moving in entourage fashion as a group. 

[BMG]

Thank you Rick, For the reasons you have listed I have been hesitaint to use this setting as I suggested. I was just wondering if anyone had tried this and tge results? 

[shadowsports]

You're welcome.  You should definitely try the feature in some mock scenarios to see how well it peforms.  People coming off a bus or subway.  People coming out of an elevator.