Netbook Sales for Q1 2009 Lower Than Expected

I was very surprised to read in DigiTimes that…
Acer, Asustek, MSI see 1Q09 netbook sales fall short of expectations
The sales figures given in the article for the first quarter of this year are:
Acer (Aspire One): 2,000,000
Asus (Eee PC): 900,000
MSI (Wind): 200,000
The article goes on to say that both Acer and MSI are looking to higher priced and higher margin ultra-thin notebook models to pick up the slack from the lower than expected netbook sales.
I wonder what the cause (or causes) is (are) for the lower than expected netbook sales: The economy is the obvious one. A comparison to conventional notebook sales might shed some light there. Has the netbook market neared saturation already? In other words, does everyone who wants a netbook already have one? Or, is it some other factor like waiting to see whether Apple enters the netbook market later this year or continues to ignore it.