This goes against the prevailing wisdom here, but Linux is not necessarily the best OS for netbooks.
The newest netbooks have about as much CPU power and memory as a notebook computer made 3 years ago. That's enough to run windows XP and older Microsoft applications such as office 2003.
And, Windows has the overwhelming advantage it always did : it has an enormous existing software library that still dwarfs that of Linux. An operating system is an enormously powerful natural monopoly. It's time to admit that the only way Linux or MacOS could ever pull ahead and have the diversity of software Windows has is if Microsoft royally screws up over a period of years. Windows ME didn't even scratch Microsoft's monopoly, because everyone kept using Win98, and it appears that Vista is the same way.
Finally, I've heard many complain that the netbook manufacturers don't properly choose a good Linux distro and configure it with all the software a user is likely to ever need. If the manufacturers did that, pre-installing open office and VLC media player and firefox and the rest, and tuned the distro behind the scenes to run blazing fast on a flash disk, then Linux might have stayed a viable option.
I would assume Microsoft has also adapated to this market : they must be offering a substantial discount on the software license for a netbook. Wouldn't surprise me if they were selling "XP for netbook use" for $20 a license. It could very well be that it is cheaper to pay Microsoft than it is to pay the technical support costs for Linux.
The MS license that accompanies Dell Mini 9s is $50 (the linux Mini 9 is $50 cheaper). I started with Windows and ended up with Ubuntu Linux. I disagree with the idea that Windows XP may be more suitable for a netbook than Linux. Try installing XP, setting up your hardware, load a few applications, and then load office. It will take a fair amount of your day. Then do the same with Ubuntu (a common choice for netbooks). I spent an hour and everything worked: hibernate, wireless, compiz for fancy window effects, and even printing to a wireless printer. If you haven't tried Linux in a while, then you should revisit soon. You will find installation, maintenance, security, and usability are all better than XP.
Lots of folks confuse bad management with destiny. -- Frank Hubbard