The archetypal way of advertising 3D monitors is by showing an object protruding past the frame of the monitor:
The problem is that this is the one thing you just can’t do on current 3D monitors—the entire effect is dependent on two images being displayed (simultaneously or in close succession, depending on the exact technology) on the monitor. Outside the frame there is nothing to display, so no image, and no 3D effect. For the best effects you want the viewers watching the image from straight ahead (not way off to the side, as shown in the pictures) and towards the centre of the screen, without moving their heads too much. That way you minimise the perspective distorsions, out-of-focus images and perceptual artefacts by the borders, where the stereoscopic effect breaks down.
But of course, in a printed image, how else would you indicate that there is something special with the screen—directly photographing the stereoscopic image would just show a non-marketable blur. (This also means that the resolution in the print image often enough has no relation whatsoever with the actually achievable resolution on the screen.)
Moral: check out the items in person, don’t go by the pictures.