"Privacy experts have raised concerns about leaks of personal information for more than a decade, said Arvind Narayanan, a computer science professor at Princeton University who has studied data mining. Careless web programming practices lead to some accidental giveaways of large hunks of personal information, he said, but other leaks are intentional.
“There’s an industry of ad targeting that tries to connect people’s online and offline activities,” Mr. Narayanan said. “People may not want all of their interests and activities and purchases to be tied together in one uber-profile that connects every dot, but that’s exactly what’s happening. These leaks are one clue to the puzzle of how companies are able to create that all-encompassing profile.”"