> the generally accepted definitions do not preclude the use of hard disks
And THAT, if anything, is what is killing netbooks.
When Asus came out with the EeePC 701, it was something truly different; 9" body (only a 7" display in that first model), SSD only, cheap. It had Linux, but even being the zealot that I am I don't consider that a requirement for a netbook. The 9xx series (full 9" display, same size body) was the pinnacle of netbook evolution from my point of view. (Arguably surpassed by the Asus T91MT, but that one had a crappy GPU which wasn't useful in Linux).
Nowadays, there are "netbooks" up to 12" in size, you almost can't find a 9" anymore, and SSD are uncommon. Basically, the term "netbook" has come to just mean "crappy laptop".