two reasons
1) she feels her macbook is a bit too big and heavy for just browsing and email - which is 100% of what she uses a computer for. TBH I think she is nuts as the notebook isn't *that* much lighter.
2) when I told her that there would be some money left over from the switch, the shopping list was already drawn up in her mind. I suggested I could add some money and get her an air, which would be just a light as a netbook and have a better screen etc. But she was already mentally buying new shoes, winter coat etc..
she doesn't care about the technology as long as it works. *I* care about the technology as I'm the one that has to make it 'just work', which will now require more effort
It'll only last for as long as I can resist buying an air on the pretence its for her :P I give it 12 months