I am not a materials engineer, as a previous poster is...
but if I remember correctly, carbon fibers not only do conduct heat, but also conduct electricity. Resin or epoxy coatings may insulate it, but I hope it insulates well... otherwise the case could do more than simply shock the user, as some aluminum and titanium laptops already have.
They could actually short out components, or create grounding problems.
Personally, I have a different approach.
Don't make parts sacrificially lighter. Make the computer have fewer PARTS.
Take the screen shell off the MBA, invert it, take the screen out of it, and take the keyboard and trackpad surface off.
Then you have the bottom of the case, the PCBs and components inside it, and an LCD screen. Discard keyboard, trackpad, hinge, screen shell, palm rest, and anything else not needed to make a computer work.
ADD a multitouch element to the screen. And a tempered, hardened glass surface, and mount it face up, where the keyboard used to be.
TABLET MBA. With bluetooth, the apple bluetooth keyboard will work with it. They could even come up with an ingenous way to clip them together for transport or use. Otherwise it is a multitouch full-OS 12-13 inch (or possibly even morphed into a smaller ~10" format, or both.) tablet PC, with extensible capabilities.
With an SSD, and no optical drive, it would have no moving parts. Just as the iPhone and iPT don't. But it would be more useable with the full version of the OS, rather than the iPhone-style embedded device type interface.
If they really want to spice it up, do a multi-touch keyboard in landscape OR portrait mode, with haptic feedback, and type directly on the screen, and only use a physical keyboard when really needed, if at all.
This is supposed to be a stripped down light weight, highly portable chassis, with a full OS installed, how would a slate tablet not serve that purpose better than a folding laptop that has more parts, two shells, and a moving hinge between them?
Give it 4 ports. 1 magsafe power. 1 high power USB, 1 miniDisplayPort external video, and 1 4-pin 1394 Firewire at FW800 speed, but perhaps not powered, if battery and space is an issue. A Gigabit Ethernet port would also be welcome, but Gigabit and FW both might be pushing it, on a thin device with Apple's current trend.
I would include them, if I were calling the shots. I would opt for one of those X-jack ethernet retractable ports, where it pops out, and you plug an ethernet cable through it, but can retract it when not in use, and it isn't a full-height hole in the side of the machine.
The first three ports would instantly allow it to connect to the new LCD Apple display, as a desktop base, either wireless or wired/full keyboard and mouse, and any other stationary peripherals connected to the display's hub.
Such a device might be a slight reduction in weight, and slightly thinner than the folding MBA that they have currently. But if light, simple, stylish, versatile-yet-minimalist, with full MacOS, is the goal... a slate would work as well or better than a sacrificially thin folding laptop, where each half is less rigid than a single piece, and the hinge is vulnerable to over extension, or being closed with something inside the machine.
This also would not replace the MB and MBP... so laptop users still would have folding laptop options...
I work with laptops for a living, in the hands of students. If it can be broken, they will break it. we get ALL KINDS of pressure spots, and broken screens from the hard use of folding laptops, and the hinges get worn over time, unless pristinely cared for. A rigid aluminum back (like Apple's new unibody structure) and a tempered glass flush front would make a VERY stiff and relatively robust chassis, compared to thinner aluminum, and plastic screens.
