Privacy is somewhat distinct from anonymity in that it refers to our ability to control who sees information about us. The sense we

have about privacy is fairly modern. In many cultures it was normal for your family, village, or tribe to know everything about you—in fact, to have a right to such knowledge.

Marriage in a medieval village wasn’t just a ceremony with a reception afterwards. The village would pretty much follow you to bed and possibly “finger the stockings” the bride wore afterwards just to make sure the marriage had been consummated. Everybody had a stake in the couple’s progeny.

Our modern notions of privacy developed in Europe and North America fairly recently. In 1890, Supreme Court justice Brandies described a “right to be let alone” in a dissenting opinion. In 1965, privacy was described as a “penumbra” of other rights. The use of the word “penumbra” suggests the difficulty that justices found in trying to found the right of privacy in existing law. The word describes one of the three parts of a shadow, the part in which light is only partially obscured. Astronomers use it to describe an eclipse in which the moon passes through the edge of the Earth’s shadow, dimming it but not obscuring it. Originally the penumbra of privacy attached primarily to the marital household, but has evolved into our modern sense of universal individual privacy.

Technology often evolves more quickly than the principles for dealing with the consequences. That 1890 opinion had to do with the emergence of photography—and that many people suddenly felt violated by having their images captured by strangers. The massive upload of information to the Internet has created a whole new realm for privacy, and this is sometimes given the separate title of “information privacy.”

The issue is somewhat complicated by the fact that we create much of that online information through our own activities. We often enjoy the benefits that come with creating a profile on a website or platform, but in doing so we’ve created more online information about ourselves.

Other information is data that, though perhaps always public, was never that accessible until everything moved online. Some of the major fears we have, that relate to loss of control over our personal data:

• Theft of information allowing others to assume our identity in order to carry out illegal activities or financial transactions.
• Wider public revelation of information that could be embarrassing or damaging.
• Tracking of information by larger entities we don’t feel comfortable with having our information.
• Government tracking of information that could be used against us in criminal or civil proceedings.
• Use of health information by entities such as health insurance companies in a way that economically disadvantages us.
• Use of personal information by employers or potential employers.

There is also a sense of possessiveness over our information. In other words, regardless of any actual threat, we feel that someone taking our information without our permission is violating some boundary.

Economists have tried to understand the level of possessiveness by looking for what kind of monetary value we might place on it. For instance, some studies have shown that people will trade off privacy for amounts that range from a few cents to $30 or more depending on the situation. Without going into details, it’s enough to say that people generally value their privacy in terms that are more economic than purely moral.

I think many of the conflicts come when we knowingly give up data, but thinking that was to a limited entity instead of some larger group. For instance, we might let Facebook post our image on a friend’s page (for their gallery of friends, for instance), but aren’t so happy when Facebook let advertisers use those same images in communicating to our friends.

On a larger scale, we may join a patient support group and share a lot of personal health information, but not be happy when it turns out an insurance company or big pharmaceutical is sponsoring the group—and collecting the data.

“Information wants to be free” is a catch-phrase that has been used by net activists in relation to intellectual property rules and information silos. But the principle is true of personal information as well. We put it out there, but many times it turns out we cannot control where it goes.