Source : WiredWired claimed to have received information on the coming MacBook Air, and decided to publish them:
As the current iMac models, the MacBook Air would be made off Alu and glass, and would be very thin; so thin that Apple would not have space to add an Ethernet port, leaving only Wi-Fi or other wireless network protocols to communicate (might communicate via FireWire if available).
This would imply that Apple would have rewritten Mac OS X to allow booting without the Ethernet address required by the system.
Last but not least, if the MacBook Air is real, its thickness could indeed allow it to be inserted in an iMac-derived docking station as illustrated recently in an App
