In the judicial backwater of a New Jersey federal court, a case is being heard that nominally affects two families but should also make millions of Britons think twice about something they do every day: put highly personal information on Facebook, MySpace or Bebo. An American insurance company, in defending its refusal to pay out a claim, is seeking to call in evidence personal online postings, including the contents of any MySpace or Facebook pages the litigants may have, to see if their eating disorders might have "emotional causes". And the case is far from a lone one. Suddenly, those saucy pictures and intimate confessions on social networking sites can be taken down and used in evidence against you in ways never dreamed of. In the US, a sex assault victim seeking compensation faces the prospect of her MySpace and Facebook pages being produced in court. In Texas, a driver whose car was involved in a fatal accident found his MySpace postings ("I'm not an alcoholic, I'm a drunkaholic") part of the prosecution's case. From Los Angeles to Lowestoft, thousands of social network site users have lost their jobs – or failed to clinch new ones – because of their pages' contents. Police, colleges and schools are monitoring MySpace and Facebook pages for what they deem to be "inappropriate" content. Online security holes and users' naivety are combining to cause privacy breaches and identity thefts. And what all this, and more, adds up to is this: online social networking can seriously damage your life. Just ask the 27 workers at the Automobile Club of Southern California fired for messages about colleagues on their MySpace sites; the Florida sheriff's deputy whose MySpace page revealed his heavy drinking and fascination with female breasts – and swiftly found himself handing in his badge; the Argos worker in Wokingham fired for saying on Facebook that working at the firm was "shit"; the Las Vegas teacher at a Catholic school fired after he declared himself gay on his MySpace page; the staff of an Ottawa grocery chain fired for their "negative comments" on Facebook; the 19 Northampton police officers investigated for Facebook comments; and Kevin Colvin, an intern at Anglo Irish Bank, who told his employers he had a family emergency, but whose Facebook page revealed he had, in reality, been cavorting in drag at a Hallowe'en party. What these and other cases show is that employers and authorities are now monitoring what people imagined were private websites – and using the contents against them. Last September, David Rice, Britain's second-ranked tennis junior, and Naomi Brady, national U-18 champion, had their funding pulled and coaching suspended after the Lawn Tennis Association found pictures of them drinking beer, partying and, in Ms Brady's case, posing at a nightclub with her legs wrapped around a vending machine. And last summer, Oxford University proctors disciplined students after pictures of them dousing each other in shaving foam, flour and silly string in post-exam revelry were found on their Facebook pages. At Cambridge, at least one don has admitted "discreetly" scanning applicants' pages – a practice now widespread in job recruitment. A survey released by Viadeo said that 62 per cent of British employers now check the Facebook, MySpace or Bebo pages of some applicants, and that a quarter had rejected candidates as a result. Reasons given by employers included concerns about "excess alcohol abuse", ethics and job "disrespect". Viadeo's UK country manager, Peter Cunningham, said the results should act as a wake-up call to anyone who has ever posted personal information online. "Millions of people are leaving personal information online, much of which is cached and remains available via search engines even after the author has removed the web page," he said. "When people who are not the original intended audience – such as potential employers – find this information, it can have a major impact on their decision making process." In America, the monitoring of social networking sites for content that may interest employers and officialdom is now so routine that software is being put on the market that will automate the process. Sure enough, software to try to defeat the snoops is also emerging – offering the prospect of a privacy "arms race" in the years ahead. ReputationDefender, for instance, offers the embarrassing personal information equivalent of credit reports, claiming it can help expunge from the online record material you regret revealing. Michael Fertik, the firm's CEO, said demand for their service is now "ridiculous", with hundreds of UK clients already. He said: "Young people today do the same thing they have always done on paper, but now they do it on a web page... The first thing we do is lobby those involved and, quite simply, ask them to remove the material by going first to the individual, then to the moderator or administrator, then, if necessary, to the ombudsman or ISP controller." What he and other experts emphasise is the online innocence of many social network site users. Privacy specialist William Malcolm of Pinsent Masons law firm said: "Rather than looking at what information constitutes a risk, it's better to think, 'Who am I sharing this information with?' If you're not sure about the identity of a third party on the website then you have to ask yourself if you would do that in an offline context, and the answer is that you probably wouldn't." Few people bother to read the fine print of a social network site's agreement, and the consequences of using one can occur in the most unexpected ways. A Newport Pagnell man, for instance, was ordered by magistrates not to contact his estranged wife, but when he joined Facebook, an automatic "friend request" was sent to everyone on his email list, including his former partner. She contacted police; the man was arrested and got 10 days in jail. The first Facebook or Bebo divorce case cannot be far away. Divorce specialist Elizabeth Allen, head of family law at Stephens and Scown, Exeter, said: "Social networking has much more scope for trouble because of the public element. It's got the potential to be more explosive. It's just like airing your dirty laundry. We've had divorces that have been due to Friends Reunited in the past and that will be replaced by Facebook with the next generation. Now most people who would never have written a love letter to someone are writing it all down and sending it because they somehow think it's different." As well as unwise posting of content, there is also an unknown but large number of people whose privacy has been compromised, or their identities stolen, as a result of their own naivety combined with the security vulnerability of the social network sites, and the willingness of others to exploit that. Last month, for example, a hacker downloaded half a million private pictures from MySpace and made them available on the file-sharing site BitTorrent. Although MySpace, Facebook and Bebo do what they can to maintain the privacy of their users, there is a constant stream of security breaches related to the applications placed on the sites. These number in the tens of thousands, most of which have been devised not by corporations, but individuals. Virtually all of them require a user to sign away various bits of personal information in return for getting the application, and, to begin work, all an identity thief needs is a name, address, date of birth, and a pet's, parent's or sibling's name. And the use of social network pages to perpetrate serious sexual or anti-personal crime is well known. Virtually every week a sexual predator is found to have used MySpace or Facebook pages to groom young girls. That something as ubiquitous as social network sites (they have 13.7 million UK users) are exploited by paedophiles and other serious criminals is not surprising. Happily, the numbers affected are small. But the use of personal page content in civil disputes, divorces, employment and legal actions will affect far more of the millions now innocently sharing their thoughts and intimate moments with the online world. A Facebook spokesperson said: "We may be required to disclose user information pursuant to lawful requests, such as subpoenas or court orders, or in compliance with applicable laws. We do not reveal information until we have a good-faith belief that an information request by law enforcement or private litigants meets applicable legal standards." In the New Jersey insurance case, involving Horizon Blue Cross Blue Shield, judges have yet to decide if they will allow the use of online postings to outweigh privacy rights. But many think it only a matter of time before such evidence is routine. Vanessa Barnett, ecommerce lawyer with Berwin Leighton & Paisner, said: "I have come across it in the recruitment field where employers are trying to form behind-the-scenes information on candidates. It doesn't surprise me that they're doing it and it wouldn't surprise me to learn that insurance companies in the UK are doing it either." Social network sites have brought unexpected pleasure to millions. But if present trends continue and users fail to wise up, the sites could soon be bringing them some equally unexpected shocks. HALKAN