I know in the pre-unibody the ambient light sensors (to control the keyboard and auto-brightness) were under the speaker grilles. One on each side to prevent mis-activation. I thought it was kind of silly, because I would always mis activate it. Now, I believe they moved them to the display on the unibody, hidden behind the glass. Where are they on the non-glossy screens? Do they have to move them back under the speaker? Surely light doesn't pass easily through such a fine grille. What about microphone and iSight light? I always marveled at how the light 'shone through' the metal on the older MBP (tiny, neural microscopic pinholes next to the camera).