MacBook Air Design Considerations
Apple WILL use flash memory. It is the next big thing in laptops and since they can't get there first, they will at least want to get there early. The idea of the Air is also to be an ancilliary portable to the desktop, not a desktop replacement.
They could use 1.8" drives, but it isn't sexy or forward looking.
Communication with the desktop is the big thing. The Air needs to be an extension of your desktop computer and communicate easily and seamlessly for the concept to work.
Ethernet dongles would be a disappointment. People always forget them.
A single dongle with muliple connectors for Ethernet, USB, Firewire, Audio might be a good compromise. Put all the connectors in one place.
Better be a 13" screen. 12" just doesn't cut it.