Who does Google think you are?

A Google tool that's been available since 2009 but which few people know about lets users see what the search giant has inferred about them based on the websites they visit. Try searching "ad preferences manager." It should be the first link. The results can be spot on -- or wildly off the mark. They're based on a "cookie," a file placed by Google (and many other companies) on each computer browser to track how its users surf the Web. Google actually knows far more than browsing histories, though. It knows what people write in Gmail messages, what YouTube videos they prefer and where they go with an Android phone. Historically, Google's privacy policies forced it to cordon off some of its most important data sources from each other, so the profile of a given YouTube user was totally separate from her Gmail profile. It was a schizophrenic view of the world. Starting in March, Google will be able to pull together everything it knows from its disparate products. Read more here