On the Internet, there's always a ghost in the room -- watching you, listening, recording your activities and interests, aggregating profiles or categorizing you, and whispering secrets and lies about you to others again and again.
It's not paranoia; you can't see them but they are there. "They" are all manner of public and private organizations, some legitimately involved with carrying your voice and data to intended destinations or acquiring records for commercial interests, others just ... listening. (Or, more precisely, sniffing.)
Some spirits -- friendly ghosts, if you like -- are dedicated to tracking actual risks, such as ensuring that stolen or dangerous materials, weapons or criminals are eventually found through their communications and movement. But others keep meticulous surveillance records of imaginary security risks -- U.S. travelers with one too many Canadian pharmacy runs or with a book by Khalil Gibran or Abbie Hoffman in their checked luggage. These are more malevolent entities, and if you saw the movie Poltergeist, you have a good idea of their potential effect on your world.
It's not the silliness of men being pulled off a plane for speaking Arabic that's frightening -- it's the insidious seepage of information between federal and corporate databases. Aggregations of unrelated risk criteria or subjective data lead to bogus correlations. Bogus correlations become inaccurate labels. Inaccurate labels become the basis for further labeling and profiling, and eventually a shoddy system breeds data with a ghostly presence of its own -- a specter that can haunt a person's reputation or bring a screeching halt to his or her livelihood.
It's no secret that being stupid with a computer these days can get you fired or worse. Anyone living in the year 2007 who's foolish enough to browse lewd materials at work or to plan a crime using a computer at the local library has a nearly inevitable date with the reaper.
But you don't have to be walking on the wild side to attract a tracker, and it doesn't take a high-profile lifestyle to find electronic eyes and ears following you around, collecting information about supposedly-offline activities. Combine it with a legal culture grown increasingly careless about traditional privacy and consumer protections, and the result is enough to give any sensible person the creeps.
For example, location and movement data for airplanes has been tracked by "black box" flight data recorders for decades. The technology made its way from airliners to commercial vehicles in the 1980s, keeping track of everything from mileage and speed to theft and contract compliance. Black boxes started appearing in fleet and rental vehicles for fraud control, and they spread slowly into production cars for other reasons, including vehicle performance and accident investigation. For example, General Motors includes event data recorders (EDR) in all vehicles now, and makes a solemn promise not to divulge tracking data ... unless someone asks for it.