There are a lot of good reasons to have a mobile device like a smartphone or MID that has a large screen. More screen space is typically very welcome when you are watching a movie or playing a game. The downside to having a larger screen is that the device is more bulky and can be harder to carry around with you. I have seen some concepts before that have dual screens and the device opens to make a larger screen for the pair of smaller ones, but they have a seam in the middle that bothers me.
Samsung has announced the development of a very cool AMOLED screen that is foldable and has no seam in the screen. This is the best of both worlds. You get a single larger screen for your content and still get the smaller profile device that is more portable. The new seamless folding screen is also touch compatible. Samsung did note according to OLED-info that while most research is going into AMOLED screens that can bend and are flexible, this foldable screen has promise for portable form factor devices.
The display uses two AMOLED panels, silicone rubber, and a glass cover along with a modular case. The prototype screen was folded 100,000 times in testing and the brightness at the center of the device where the two screens meet was only reduced by 6%. Samsung has shown off something similar to this as far back as 2008. The video below is that 2008 demo and you can clearly see the seam of the displays. The new screen won't have that seam.