There is, it turns out, something worse than being dragged through a messy divorce in court - being dragged through a messy divorce in cyberspace. A 52-year-old Englishwoman in Manhattan has been extending the frontiers of gossip ever since her wealthy husband, a titan of the arts establishment a quarter-century older than she is, decided he wanted a divorce. The woman has told reporters the press is stacked against her. Since April, she has posted three videos on YouTube about her marriage - with details of Viagra, condoms, pornography and someone she calls a "nasty evil stepdaughter" - and they have got 4m hits.

Most talk about internet privacy involves either government spying or hackers using "Trojan horses" to steal your credit card information. Stories such as the YouTube divorce show that the internet's challenge to privacy is broader. You do not even need to own a computer to have your dirty laundry hung up in cyberspace.

The problem is not new technology but the way it interacts with old-fashioned gossip. In his recent book The Future of Reputation*, the US law professor Daniel Solove shows that online gossip is not simply offline gossip with a few extra people listening. It is something qualitatively different. A South Korean woman was written up as "dog-poop girl" in newspapers all over the world after she was videotaped cursing fellow subway passengers who complained about her dog's behaviour. But one need not do anything wrong to gain infamy. A Canadian boy who lost track of the videotape he made of himself acting out an episode from Star Wars has been ridiculed by millions. Online gossip can be damaging even if provably false. In the US Midwest, a woman wrongly identified as a professional basketball player's rape victim found herself featured on a page captioned "Whore Alert".

Purposeful web-users have channelled this power to break reputations into a force for social change, in a way that Mr Solove calls the "cyberspace equivalent of mob justice". Waitresses have databases of bad tippers. Online daters have a blacklist of bad men called Don't Date Him Girl. Doctors set up a registry of patients who have filed malpractice suits called DoctorsKnow.Us. For the first time since the birth of the penitentiary system, Mr Solove notes, punishments relying on shame and stigma are on the rise - although probably the internet is only partly to blame. Shaming punishments are also a good outlet for the "creativity" of egotistical judges, such as the one in Arkansas who, several years ago, ordered a woman guilty of driving without a child safety seat to write a mock obituary of her child.

The internet is the wrong place to punish people. Since internet data are permanent, the shame inflicted on trespassers is, too. Gradual maturation and mending of ways, by contrast, are not considered newsworthy. An ordinary person, such as the dog-poop girl, is unlikely ever to do a second thing to become world famous. The internet has thus placed her, as far as the public is considered, beyond redemption.

Dangers to reputation are particularly acute in the US, where protections for confidentiality, weak to begin with, have been further weakened in the internet boom. Many US internet laws were enacted in a burst of giddy libertarianism in the mid-1990s. Mr Solove zeroes in on one in particular that has wrought a lot of misery: section 230 of the 1996 Communications Decency Act, which holds internet service providers blameless for any defamatory or invasive information they purvey.

The result is that some shocking acts of indecency are met with indifference, even after repeated complaints. (Mr Solove cites the jilted man who opened a Yahoo account in his ex-girlfriend's name and posted nude photos of her alongside her e-mail address.) One does not want to over-regulate online business, but someone should be responsible for purging such attacks more aggressively. When it is copyright, not privacy, that is infringed, Mr Solove notes, internet service providers police violations with lightning speed. If privacy rights were treated more like property rights, abuses would wane. Mr Solove also argues the US should follow British law's willingness to rule against "betrayal of confidence".

There are never perfect solutions to problems of "data ecology". One of the most radical and appealing recent ones - because it addresses the problem of permanent data - has been set out by the Harvard public-policy intellectual Viktor Mayer-Schönberger**. For most of human history, data that no one made an effort to remember were automatically forgotten, he notes. Today, data that no one makes an effort to forget are automatically remembered. He suggests using law and technology to create a "forgetting" internet - by, for instance, using the meta-data attached to all computer files to erase most data after a given period of time.

The basic barrier to the malevolence of an organisation such as, say, the Stasi was that storing, retrieving and making sense of lots of personal data required more manpower than society possessed. That barrier has been overcome, with dangerous results. Naturally, when so many people profit from breaches of privacy, we are encouraged to distrust it - who would want privacy but a terrorist or a pervert? Yet privacy is the realm in which personal convictions ripen into public engagements - no privacy, no democracy. To judge from the amount of information shared online, people are not yet terribly worried about privacy. That is another way of saying they are not terribly worried about liberty.

*Yale University Press, $24/£16 **Useful Void: The Art of Forgetting in the Age of Ubiquitous Computing. Available online at ksgnotes1.harvard.edu/Research/wpaper.nsf/rwp/RWP07-022

The writer is a senior editor at The Weekly Standard