FIPR point to Cryptome on Friday last -

"One problem that most naive paranoid types completely fail to grasp is the titanic volume of modern communications. The flow
is so overwhelming that only a powerful God could possibly process it all to find interesting material. The entire federal budget
could not pay enough humans to screen and analyze ALL the electonic communications of even a medium size city in 2003.
So communications intercepts are necessarily targeted very narrowly, even drag net fishing is likely done only in places where
there is a real likelihood that something important will turn up with finite effort.

The notion that an all powerful big brother is listening to everything and capturing everything just is not realistic, and a very very
high percentage of what does get captured is never looked at or listened to or even stored for very long."

Only the practioners really ever understand the limitations of the technology - drinking from the firehose being one of the most obvious....