Just out of curiosity, what does one do for major OS upgrades, or full reinstalls (well, I haven't had to do that on a Mac since... since I can't remember) if you have a MBA and no other computer to share the disk from?
I'm assuming you have to have an external optical drive available to plug in? I would think Apple can't really get rid of the optical drive until they solve this problem and I'm not sure the world is ready for OS installs over the Internet. I suppose they could throw it on a little USB drive, but that wouldn't be the cheapest solution, especially for upgrades.
This was solved eons ago, it's just hasn't been used by Apple yet. I already stated how it's trivial to copy your Restore Disc to another drive. Compared to the cost of a DVD drive used in Mac notebooks the cost of a USB or SD card is less. And that's without considering the limitations an optical drive adds to engineers of modern computers.
Imagine how much smaller an Upgrade Disc box would be if it came as an SD card (which Apple oddly added to their machines so late in the game)?
Apple is in a unique position in that they can afford to do this better than other OEMs. The HP Envy's don't come with internal optical drives, yet the Windows install discs come on a DVD. Oddly, they do come with a 2GB SD card containing the User Guide.
We can argue that the price per machine is still too high. I can find 8GB SD Card for $8 retail and I'm sure Apple can get cheaper, slower NAND than that. That's beside the point since Apple hasn't enacted this option. The optical drive going away in notebooks and NAND getting cheaper are inevitable. They still have a couple Macs that don't have SD card slots yet. If the next Mac Mini, MBA and even Mac Pro get SD card slots then I think we shouldn't be surprised to see the next version of Mac OS X be shipped on SD cards and as optical discs.