How does one walk using it? I may be overlooking something, does anyone know?

The Half-Life video a couple months back had a guy leaning forward to walk forward

Depends on what kind of game.

My guess was that such movements would have required voice commands like "walk" and stuff. In order for Natal to recognize that it must be really accurate, seems interesting. My doubt has always been: what happens if someone walks in front of you? How can I prevent that the clowns that are my friends decide to mess with my Natally-gaming experience by messing with the camera without resulting in subsequent fist-fights and blood n' gutz exposed?

Edit: My one guess is that you "scan" yourself with the camera so that the game recognizes you and only you. But what if I change my clothes? Do I need to scan myself again?

leaning should be able to do it, but that's a pretty sucky solution.
Maybe the position of your hands relative your body or something.

I don't know. I keep trying to imagine hoe I would play halo with leaning, but I keep forgetting that it will have its own games beside Halo.

who cares it's black & white game or nothing.

It's completely up to the dev. Putting about 30 seconds thought into it I came up with two decent options - leaning (it's already been said, I know) or the position in which you stand - when it loads up, the distance you are from the tv is the neutral position, stand closer and you walk forward, stand further and you walk backwards

The companies using Natal are going to put thousands of man hours into picking and optimising their method.

All will be fine

Grab a controller while using it.
or like people said act like an old man and lean forward (but where did they show that?)

Thumping your feet c

I figured it out moonwalk cause this is thriller. sorry wrong thread.