I guess I shouldn't go further than that. E.g.
...a classic example: A lady had been to a school play the night before, and her son was in the school play and she thought he did a lousy job. Next morning, she was talking on the telephone to her friend, and she said to her friend something like this, 'Oh, Danny really bombed last night,' just like that. The computer spit that conversation out. The analyst that was looking at it was not too sure about what the conversation was referring to, so erring on the side of caution, he listed that lady and her phone number in the database as a possible terrorist.(60 Minutes Transcript, 2000)
Given this type of spying when 9-11 hadn't even happened, civil liberties groups moved to impeach Clinton.