Look, if a user's browser provides the CPU ID number, any Web site can collect it. That means any unsavory Web-site owner can hijack that CPU ID and use it with a specially modified browser to impersonate the original user. Then again, it's not the horrifying, world-ending threat that privacy mavens make it out to be, either. Nobody is anonymous on the Web except maybe hackers who carefully cover their tracks. Web servers log each user's IP address.
Internet privacy is already rare, and Web anonymity nonexistent.
As a threat, CPU ID is just one more drop in the bucket. All of which is really beside the point. What makes Intel's new CPU serial number a good thing is that it's just that a serial number. Sure, it may be a bust in E-commerce, but it still can be handy for keeping track of PCs inside a corporate IT shop. So turn on the CPU ID feature to log PCs when they arrive.