That's actually not quite correct. The wheel still physically moves as it does on the Mark II, but now also includes the touch controls for video. And Thank God for that, I hate touch sensitive scrolling. It always makes it hard to select things and would be tough to impossible to use with gloves.
Look at 1:18, doesn't look like the wheel is moving to me. I know it has that lock switch below it, but it doesn't appear to be engaged.
Canon EOS 5D Mark III Preview by dpreview.com
Then at 1:31 in this video it refers to the wheel as "touch pad"
EOS 5D Mark III Walkaround COOL!
i've read other reviews though that specifically say the wheel now does both. plus he was controlling video volume levels, exactly what the touch sensitiviy was added for.
but think about this: if the wheel is purely touch sensitive, why does it have those grippy teeth on it still? if it was touch only wouldn't you think they'd take those off? teeth don't make sense when you're using a touch wheel that's supposed to be easy to slide your finger around.QuoteWhile the rear command wheel turns as normal, making a clicking sound as it does, it also functions as a touch-sensitive d-pad for silent use when shooting video.- hardware zone's review http://www.hardwarezone.com/tech-news-canon-5d-mark-iii-announced-brand-new-22mp-sensor-and-digic-5-processor
Silent control with Quick Control Dial – during actual recording:
Both new high-end EOS models have a newly-engineered rear Quick Control Dial. In addition to its conventional rotational operation, a new touch-sensitive technology has been developed. This allows the video shooter to make selections of what he or she would like to adjust – ± exposure compensation, shutter speed or aperture adjustment, manual audio recording level, or ISO setting. And, by just lightly tapping on the left or right side of the inner surface of the Quick Control Dial, its new touch-sensitive capability lets users silently make these adjustments, without the audible "click" of normal dial rotation. Two steps are required: make sure Quick Control Dial/silent operation is active in the video shooting menu, and then during recording, press the "Q" button to call-up the on-screen displays. Tap up or down to select the option to be changed, tap left or right to actually change the setting.