MacBook Air was launched as the world’s thinnest laptop and to do that Apple had to sacrifice a bunch of things to keep both weight and size at a minimum. We can imagine that the optical drive was one of the first to go, but to compensate Apple launched an external SuperDrive, specially designed for MacBook Air. It carries the same slim and clean design, and it only works with Air. If you connect it to another computer it won’t work.
Apple had to tweak the USB port to supply the SuperDrive with enough power. Physically the USB port of MacBook looks like just any USB port, but since a regular USB can only supply 500mA, which is not enough for an external optical drive, the USB port had to be tweaked for more power. This was investigated by the people over at Engadget. The SuperDrive simply refused to work with any computer but MacBook Air, which is quite logical in retrospect.
They’ve also published this rather hilarious picture of what will happen when you try to use an USB Modem with MacBook Air (it lacks an internal modem).
