Google keeps a vast amount of user data it tracks in silos, according to Re/Code. Now, Google "is rolling out a new service that pools data from across the entire web and mobile devices, giving it a potential boost to its core ads business. The big caveat: It’s giving users total control — and with that, they’ll have carte blanche to block particular ads." This is one way for Google to get ahead of the growth in ad blocking, and "by building the feature opt-in, it’s also a way for Google to combat criticism of its privacy practices. Starting today, its billion-plus users will start seeing a notification in Gmail or Chrome about a new privacy update."