There were stories that NSA computers were keeping track of anybody who used certain words over the net during the clinton years, and the FBI set up some big computers too. I don't know how much of it was true (how would anyone know?) but there was plausibility.
This also covers most phone conversations because of the use of wireless relays.
Try doing a google search of "NSA eavesdropping."
Google "Echelon"...that's NSA's snoop stuff......some claim it can tell when your pop-tarts are done in your toaster oven.
FBI's "Carnivore" pooter sniffing program had a name change to a soft and fuxzzy title like DSC2000 or something like that....
All this data collection isn't worth a hill of beans unless you have the eyeball power to analyze it.