Exclusively multi-touch interfaces have only limited applications at sizes much bigger than an iPhone. Something the size of a piece of paper doesn't seem big,

Exclusively multi-touch interfaces have only limited applications at sizes much bigger than an iPhone. Something the size of a piece of paper doesn't seem big, but it'll certainly feel big if you've been moving your hands all over it for a couple hours. Most people set up their mouse so that a few inches of hand movement will take the cursor from one side of the screen to the other. Having the size of a movement scale 1:1 to its on-screen representation would get tiring pretty quickly.