The Apple eMate was arguably Apple's first foray into the Netbook category:
It was out when PalmPilots were the newest, hottest computer gadget running.
The MacBook Air, though, does seem like it follows more of a Netbook design philosophy. Compared to the rest of the lineup, it's pretty minimalistic and more portable. But, as mentioned above, it's a nicer than most netbooks out. It should be, with the pricetag!
Apple's always been pretty progressive. If you think about it, how often do you actually NEED your CD drive? Sure, for burning CDs and importing music, but do you NEED to do that on the go, or can you do it at home with an external drive? Don't most people buy from iTunes or other online music sellers nowadays? Who buys hardcopy CD albums, aside from hard to find stuff?
They did something similar with the 3.5 inch floppy drive on their older laptops--just replaced it with a CD ROM drive, years before CD's and CD:RW's bumped 3.5's out of usage.
Will the MacBook Air be disco'd? Probably. Apple has a history of offering amazing models that are ahead of their time, then scrapping the design when they can't find a market for it instead of refining it.
Personally, I'd love to see a tablet/laptop format jumbo iPod Touch model. Or, at the very least, an external keyboard for the iPod touch.