There is a good post about skeuomorphs titled Skeuomorph, Pt III.
Also, next to touch and smell, there is another problem with skeuomorphs on digital screens. Changing the view angle. When moving your head, everything stays the same. It doesn’t change the 3D perspective, it doesn’t change the shadows and highlights. It still feels like a flat picture of something 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.
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 II: Seems Apple is already working on it.
Update III: In iOS6, when tilting the divice, the metallic slider-thumb changes reflection.