bleirer wrote:
I think people do it mostly to save battery. But it would have to be situational. It doesn't disable any features, though. With continuous AF 'off' it only autofocuses with a shutter half press or equivalent. With it 'on' it focuses all the time the camera is on, until the camera times out, even when the camera is swinging from the strap. I'm not sure if it has any impact on IS, though, so probably a moot point.
DLSRs in general, and EOS equipment specifically, don't show a measurable battery issue with IS-enabled lenses. The most effective way to save battery is avoid image review & clean-up, a battery resource waste. Similarly, focusing and shooting in Live View will run down the battery way faster than otherwise.