The civil rights campaign group Liberty is firmly opposed to what Mr Cameron wants to do, saying blanket surveillance like that would just create a huge "haystack" of data and make it even more difficult to monitor real suspects properly.
But terrorists hide like needles in the vast haystack of the innocent majority.
Teams can search and search until they find the needle in the haystack of data that confirms a player is who they want him to be.
The agency is under rules preventing it from investigating that so-called haystack of data unless it has a "reasonable, articulable" justification, involving communications with terrorists abroad, he added.
Why not let the agencies collect the haystacks of data so they can look for the needles within?
The trouble with seeking a meaningful needle in massive haystacks of data, says Trevor Hastie, a statistics professor at Stanford, is that "many bits of straw look like needles".
Computers can store vast amounts of data.
He assimilates vast quantities of data.
Instead, astronomers are now faced with vast quantities of data.
