As any writer, teacher or politician knows, definitions are important. How we define something -- heck, how we name it -- often colors how we think about it. And as a result, those who want to influence the way we think about something, will often try to define what we call it.
For example, those of us who read (or write) science fiction have gotten used to literary figures redefining science fiction and fantasy to make sure their own writings don't fall within the despised genre. The Ansible newsletter, which details the activities of British SF fans, includes a category called As Others See Us, which points out all those who redefine the works of, say, Philip K. Dick as not "sci-fi" because he was really a "serious writer."
In the same way, I've enjoyed the back and forth about Apple's new 11.6-in. MacBook Air. It is smaller, lighter, less powerful and less expensive than other MacBook notebooks. But don't call it a netbook.
Why? Well, just like it's important to many "real" writers that they not be considered part of the science fiction genre (because anything that falls into that category is, by definition, bad), so it is important that the Air not be considered a netbook because, as Apple representatives have made clear, netbooks are nothing more than cheap, badly-made laptops and not worthy of consideration.
As a result, when Apple came out with a notebook that was smaller and lighter than its previous models, and which compromised on such features as processor and memory in order to hit a price point below $1,000 (which, for Apple, qualifies as less expensive), it was important that Apple reassure its customers that the company had not created a netbook.
Of course, it's hard to define something as a netbook when there isn't really one definition. Personally, I tend to see netbooks as notebooks that are under 4 lbs., have displays that are less than 12 in., and that are reasonably inexpensive. Under that definition (assuming that $999 is "reasonably inexpensive" for an Apple product), I might classify the new Air as a netbook.
However, at least one other company would agree that the new MacBook Air isn't a netbook. When Microsoft came out with Windows 7, it included an iteration called Windows 7 Starter, which was aimed at netbooks. In order to keep the lower-priced Starter out of the majority of PC systems, Microsoft was strict about the specs of the devices it could be loaded onto. This meant displays no larger than 10.2-in., up to 1GB of RAM and a maximum 250GB hard drive (or 64GB SSD).
So by Microsoft's definition, the new MacBook Air is definitely not a netbook. Which may be one of the few times Microsoft and Apple have agreed about anything -- at least, in public.