That's not really true. AO is not effected by the direction of the light. If you turn it on for a diffuse light (A perfectly valid setup BTW) the back of the object will be darker, only because there is no light coming from that side, not because the AO calculation in effected.

Look at the image above. One Jessi is rendered with the light dead front. The other at stage right. Which is which? I can't tell either. One light, a solid white IBL with AO on.

Shadow can also be turned on if used correctly. It's really easy to get them right too. In the material room pick the IBL light. Look at the IBL image. See where the sun is? Setup the light so it's in the same place on the light ball. Now set the shadow level low, maybe .3 I usually use mapped shadows, but you can try raytraced shadows here as well. Either way you will probably wan to make them nice and soft with a blur of 2 or 3. In the picture of Leela above that is the setup I used.

Nerd3D