I would guess most home internet users could be uniquely and instantly identified by their IP address. Google, Facebook, the NSA, Experian, Transunion, Equifax, no doubt many other entities could run this function: identify_home_user(1.2.3.4) and get your name, address, SSN, etc. Even if the identification is not unique, it probably narrows down to a married couple, rarely as many as 5-6 adults. That's pretty good ID from one number.