Ughhh. I hate these comparisons.
Netbook sales are dying down because more people who want them now have them, as time goes by. This is a natural progression of sales - same thing is happening with the iPhone.
I won't buy an iPad, because it doesn't have what I need/want. I don't want a closed system, I want to install, run, what I want. I also want a very portable form factor. Speed and power are not that important, since this is a secondary machine - used mainly for browsing, email, youtube, etc.
What I want, like may others, is a Mac netbook, running OS X.
...So I got one

Picked up a Dell mini 10v, and an hour later I had a mini macbook - everything works flawlessly. And, it cost $250.