The personal computer is the default device for computing, period. Other devices are used only for convenience or emergencies. We are all comfortable with PCs, and they have become part of civilization comparable to the automobile. Microsoft has been successful marketing to the vast and ever-growing world of PCs with applications and tools. The final bug in the .NET ointment will be the public perception of Microsoft as a sneaky company.
People dislike being monitored.
This is not because they have things to hide but because it's just plain creepy. Have someone stare at you while you're driving, for example. See how you like it. Background monitoring by a computer is similarly creepy. There is a distasteful aspect to the idea that Microsoft does not fully understand.