Companies can sell data about what products people buy, where they vacation and where they invest. But disclosing what videos people rent was made illegal after the rentals of Supreme Court nominee Robert H. Bork were made public during his unsuccessful 1987 confirmation hearings.
In roughly 20 states, drivers' license records are public information. This is how direct marketers can know how tall people are, how much they weigh, whether they wear glasses and, in many states, what their Social Security numbers are.
Political activists use these lists as well. In his book "Closed: 99 Ways to Stop Abortion," anti-abortion advocate Joseph Scheidler urged fellow activists to write down the license-plate numbers of cars parked at abortion clinics, get the names and addresses of the owners from the state motor vehicles department and then picket their homes and deluge them with mail.
California stopped selling its motor vehicle records after a stalker used them to find and murder actress Rebecca Schaeffer in 1989.
There are many legitimate uses for this information. If driving records were private, for instance, school bus firms might not be able to check the driving records of job applicants.
But policy toward what should be available and what should not is all but nonexistent, privacy advocates say. In Europe, by contrast, there are laws that precisely detail how the technology can be used.
"To some extent, we are first in technology and last in privacy," said Marc Rotenberg of the Electronic Privacy Information Center.
A U.S. data protection board with advisory powers was proposed in Congress in 1991, but has not materialized. And other legislation to deal with monitoring at the workplace has been stalled in Congress for years.
A bill sponsored by Sen. Paul Simon (D-Ill.), for example, would require employers to disclose in advance that workers might be monitored, that the monitoring would be for business purposes only and that certain places, such as restrooms, would be off-limits.
Increasingly, the home is another area of concern. When the age of interactive television arrives in perhaps five years, what policy should there be governing how data on viewing or shopping habits can be used?
It's a question to which scholars, public policy-makers and businesses have given little thought.
As Marx at the University of Colorado laments: "There hasn't been a lot of careful research into the social implications of all this."
Always Under Watch: A Day in the Life...
Whether by video camera or computer, surveillance techniques may threaten your privacy. Here are some of the ways:
1) THE COMMUTE: Cameras on freeways catch a driver speeding to work.
2) AT WORK: Parking garage video camera can note a worker's arrival time, companions in auto.
3) WORKSTATION: Employers can monitor computer messages and other electronic work.
4) AT LUNCH: A diner's credit card scan shows restaurant and bill.
5) AFTER-WORK ERRAND: ATM camera and computer records transaction. Credit card used at store shows where consumer shopped, what you bought.
6) DRIVE HOME: Toll booth scanner records when auto passed.
7) IN THE HOUSE: Shopping by phone gives companies information on tastes and lifestyle.