I agree with mpasternak. This is no different than 95% of the cellphone plans in the USA. People these days think nothing of getting a 3G high-end cellphone for free or less than $100. They simply fork over the monthly fee for the service.
Selling cheap, or giving away free, netbooks is just the natural extension of that.
As for who would buy them, I see the majority of customers being of the typical cellphone user. Non-technical people who simply want a full-time internet connection at home and on the road along with a cheap laptop. Since most of us technically inclined people purchase our own Internet connection and computer equipment separately we not only understand the details involved but we also enjoy the freedom of choice available. The standard individual though would probably benefit from this.
Actually, this is nothing new in the computer industry either. For years AOL, MSN and other Internet ISP companies have tried to sell cheap computers in the stores requiring you to sign up for their 2 year online service.