There is a good post about skeuomorphs titled Skeuomorph, Pt III. 

Next to touch and smell, there is another problem with skeuomorphs on digital screens. Changing the angle you look at it. Moving your head doesn’t change the 3D perspective, holding your tablet in a different angle does change the shadows and highlights. It just feels not as real.

Maybe one day we can add a bump map to create more dynamic shadows/highlights and a screen surface that sticks out. We might also get multiple light sensors so we can adjust according to our real light sources. How cool would it be to move your tablet closer to your lamp and see the shadows and highlights change.. woaaahhh…

I’m not entirely against using Skeuomorphs in our designs. I do it too. Without being able to use textures and fake 3D it would quickly get boring. But maybe something to keep in mind: Using Skeuomorphs on desktop screens are way less problematic than on tablets or phones because on desktops you don’t touch it with your finger and you mostly keep a straight angle.

Update: @apexsier points out that such a directional light sensor is called Light Field Sensor and already in use by the Lytro camera. 

Update II: Seems Apple is already working on it.