"The [National Security Agency (NSA)] agency’s ability to efficiently mine metadata, data about who is calling or e-mailing, has made wiretapping and eavesdropping on communications far less vital, according to data experts. That access to data from companies that Americans depend on daily raises troubling questions about privacy and civil liberties that officials in Washington, insistent on near-total secrecy, have yet to address.
“ 'American laws and American policy view the content of communications as the most private and the most valuable, but that is backwards today,' said Marc Rotenberg, the executive director of the Electronic Privacy Information Center, a Washington group. 'The information associated with communications today is often more significant than the communications itself, and the people who do the data mining know that.'
"In the 1960s, when the N.S.A. successfully intercepted the primitive car phones used by Soviet leaders driving around Moscow in their Zil limousines, there was no chance the agency would accidentally pick up Americans. Today, if it is scanning for a foreign politician’s Gmail account or hunting for the cellphone number of someone suspected of being a terrorist, the possibilities for what N.S.A. calls 'incidental' collection of Americans are far greater.
"United States laws restrict wiretapping and eavesdropping on the actual content of the communications of American citizens but offer very little protection to the digital data thrown off by the telephone when a call is made. And they offer virtually no protection to other forms of non-telephone-related data like credit card transactions"(http://www.nytimes.com/2013/06/09/us/revelations-give-look-at-spy-agencys-wider-reach.html?hp, accessed 06-09-2013).