Concerning flash drives in netbooks: as the driving feature of netbooks tends to be price, you'll normally end up with a pretty low-end solid state drive, which don't tend to give you the speed advantages over hard drives that more expensive solid state drives would.
I would say that 8Gb is fine if you're not going to be installing a lot of software, or don't want to store a lot of music, pictures or video on it. If it is intended to be your primary PC, 120Gb might be better.
As always, whatever size of drive you have, make sure that you regularly back up your important data somehow!