I read this as tongue-in-cheek at first (since most web sites do their darnedest to track their users, and having a log-on kind of requires this anyway).

A centralized authentication system like this wouldn't need to be a single consistent UUID per person which was then passed around. Presumably you'd have a central login to authenticate you to the system, and then the system could create separate 'id' tokens per web site or whatever that the user logs in to.