for nearly a decade, Google did in fact keep DoubleClick’s massive database of web-browsing records separate by default from the names and other personally identifiable information Google has collected from Gmail and its other login accounts.
The practical result of the change is that the DoubleClick ads that follow people around on the web may now be customized to them based on the keywords they used in their Gmail. It also means that Google could now, if it wished to, build a complete portrait of a user by name, based on everything they write in email, every website they visit and the searches they conduct.
The move is a sea change for Google and a further blow to the online ad industry’s longstanding contention that web tracking is mostly anonymous.
A super-scary news via Google Has Quietly Dropped Ban on Personally Identifiable Web Tracking