[citation][nom]alvine[/nom]how can you aim with the bar in the middle of the screen?[/citation]
The middle bar would be a huge inconvenience for any FPS or other game with a centered crosshair. That's exactly why three displays in portrait mode, with an undisturbed HUD on the center screen, makes a lot more sense than six displays, or any other configuration that breaks the center of your overall display.
And, as mianmian mentioned, even thin bezels around LCDs makes for an unpleasant viewing experience, in my opinion. The extra real estate might give you a competitive edge, but it just doesn't look good to me.