Earlier quoted context omitted.
This could be a little more intelligent. E.g. a coffeeshop has a constant stream of accounts on its IP that appear only once or twice. So it might be considered "a public place". So no association is done over accounts arriving from that IP. Your home, OTOH, might have only two accounts on its IP for years, so the association here is stronger. A cookie shared between two accounts is even a stronger indication, as a p…
Sure it could be more intelligent, but there would always be false positives. For example a Google employee's spouse could likely get correlated. False positives sounds like a bad idea for a system that tries to match personal and work accounts. Also in my case it would be harder possibly because I have a ton of personal Google accounts. >A cookie shared between two accounts is even a stronger indication, as a person…
In short, the amount of data you are passing to Google, willingly or not, allows them to link these to a single person — you — with an extremely high certainty.