When the first netbooks arive I had an idea. I would use it as expected as a portable computer for browse or other stuff low performence stuff.
BUT when I am at home, would use it as a home server. I would boot it from a SD card or CD and plugin a USB-HDD drive. Due to low energy consuption and noise it would be a good "home" server, storage centre running 24/7 with a good UPS :D
So I would have both a good portable device and also a little server. Due to different boot devices/storage I would not have to do any "special" modification when going out or returning.