The ideal of ad-supported Windows makes perfect sense under a number of different circumstances. While it most likely won't be appearing in any offices, it would be ideal for libraries, internet cafes, and in the homes of casual users. The Windows kernel would probably not need much work judging from how well some spyware/adware manages to integrate itself, though users would have to ensure at least occasional internet connectivity in order to allow Microsoft to track advertisements and make new ad units available. This tracking would certainly open the doors to some privacy question, but this would probably be a sacrifice users are willing to make in order to get a cheap, or free, OS. The question of privacy will become enormously more important as advertisers want increasing amount of targeting information about users in order to make their advertisements more effective.