http://en.wikipedia.org/wiki/Utah_Data_Center -- 'alleged to be able to capture "all forms of communication, including the complete contents of private emails, cell phone calls, and Internet searches, as well as all sorts of personal data trails—parking receipts, travel itineraries, bookstore purchases, and other digital 'pocket litter'."'.

That page talks about being able to store (hypothetically) 1 trillion TB.