Think of it in terms of Big Oil, Big Tobacco, Big Media, Big Government, etc.
Big Data represents companies with huge amounts of data that know or can forecast things which we hadn't realized before. Google and Facebook know people's habits, history, and interests across the Web. Bit.ly announced a service, last year, where they can predict which stories will get the most attention over the next 24 hours and act on it. There is no shortage of examples of how this data is being used.
While Americans are sensitive to privacy concerns, it doesn't compare to most of the EU. And the EU's concerns are valid given their history over the past century. Social networks, created by analyzing telephone billing statements during WW II, were one way that Germans could connect, say, political figures with individual citizens of the cities they invaded.
It's one thing for an individual to control who they connect with publicly or on the Web; but it's another thing when it's happening without your knowledge.
While I live a fairly public life on the Web, it's my decision to make my private life public. I can't imagine what it's like for celebrities being hounded by the paparazzi – I'm sure that
lack of privacy grows old, fast.