Sorry, I actually don't see it... At least not in a very significant way. The reason why we see 3d is because we have two cameras (eyes) side by side looking at objects from slightly different perspectives, right? I'm no expert, but one stationary camera with one dude moving in front of it shouldn't cause a stereoscopic effect even if you take two frames of it (unless he's rotating, maybe).

It's kinda like having an image of pacman with his mouth open and another with his mouth half way closed, crossing you eyes and saying you see him as a sphere. Edit: Or, they wouldn't need special stereoscopic cameras for movies, they could just play two of the same videos one frame out of sync and call it a day. Maybe?

If an expert can prove me wrong, I'll shut my mouth.