nagromme said:Lap, desk, hands, or whatever... 18" is about how far away a portable device is while in use. Portable devices won't replace movie theaters, obviously. But they can provide a viewfield similar in size to home TVs--that's what I was surprised to discover.
I agree with Nagromme. To the person who thinks 18 inches it too far away, think about how silly we would all look holding screens right up to our face. I think most people hold a PSP or other portable video devices close to 18 inches from their face. 18 inches really isn't that far.