I think you were just trolling, but the GP was asking a very pertinent, reasonable question specifically about companies like Facebook, Google, etc, and how they differentiate. Your reply -- ostensibly about what an organization like the FBI might do to identify someone -- is not relevant to their question at all, making it all the more bizarre that you decided to question whether they were "trolling" (apologies to all others, but that is a growing peeve of mine -- this noisy declaration of things people say as trolling).

Google knows a lot about someone, but they have no idea what citizenship I hold. They can guess, of course, but that isn't a lawful way to discriminate.