What is missing in this image that stops it from looking like a photograph? Look at this image:

This is CG, Saya, a project meant to make as real CG as possible to the point of becoming indistinguishable from reality. I would say that it is pretty believable. But, it still doesn't seem real enough, something's missing. And I don't know what it is. And it drives me nuts. 

I am not saying that CG has to do reality, I am personaly fond of stylization, but I really want to know why we can't get a 3d image just right yet.

Is it the light? The clothing? The lines above the lip, too defined?

Any insights would be appreciated.
The hair seems to have sampling noise or aliasing in it. This might be poor jpeg compression but it does not look like it.
I've never seen hair part that way (could just be me).
The neck looks a little too regular (I'm no modeler though).
The skin's subsurface scattering falls a bit short. Perhaps it's not that but there is something slightly off about the skin.
The shirt has a slight plastic feel to it.


Most of this is entirely subjective of course. I think it's fairly good but falls short of the state of the art in many areas.