A DECADE ago, Shane Warne's sexual misdemeanours - which, incidentally, seem to have cost him his marriage - wouldn't even have been possible.

The rules of flirtation have changed dramatically. SMS, email and the internet chatroom have opened up a brave new world of amorous communication, and both men and women are reaping its benefits - and suffering its sometimes disastrous consequences.The new digital lexicon is rich with witticisms, innuendo and socially acceptable flirtatious behaviour, with the added bonus that indiscretions are, well, discreet. You only have to visit an internet chatroom for a glimpse into a world of horny acronyms and obscure propositions. So let's get down to it: IYKWIMAITYD* ...

It's a wonder most Australians aren't getting repetitive strain injury. Consider the figures: according to a 2003 Australian Communications and Media Authority report, 72 per cent of the population over the age of 16 use a mobile phone; more than 250 million SMS messages are sent every month; and the internet now attracts a whopping 13,991,587 Australian users. Work, of course, accounts for a fair number of the times we hit "send and receive", but more than 60 per cent of respondents in a 2001 Gallup Poll said they most often emailed friends or family. It's increasingly clear that many of our daily interactions happen from within the construct of a virtual world.

Make no mistake: cyberspace (as William Gibson pointed out when he coined the term in his 1984 book, Neuromancer) is not the real world. Which is exactly its appeal for many online and mobile-phone users. This sense of being in a parallel universe (with its conveniently flexible moral boundaries) may explain why it seems appropriate to sign off with an affectionate "xx" - even when the recipient of said affection is someone we wouldn't pucker up to in a million years. Kate Fox, co-director of Britain's Social Issues Research Centre, describes cyber communications as occurring in a "liminal zone", that is, a well-documented phenomenon "in which normal rules and social constructions are suspended". Strange things happen in liminal zones: public nudity at Mardi Gras, self-mutilation during tribal initiation ceremonies and drunken revelry at Schoolies' Week are some real-life examples. Yet to the individuals involved, their behaviour feels normal - because it's acceptable within that zone. After interviewing 1000 people about their flirting habits, Fox found that all respondents, without exception, claimed they'd say things in cyberspace that they would never say face-to-face. "It's a little bit like being drunk," one person explained.

As a dating tool, it could even be considered quaint. "In some ways, cyber-flirting is also a return to a more old-fashioned style of courtship, in which prospective partners spent rather more time getting to know each other and writing love letters before jumping into bed together," says Fox. On the other hand, it can also be akin to having a virtual harem ready to lead you astray.

Consider newspaper personals, once a rich forum for traditional hook-ups with strangers. Few of us can resist browsing those sometimes poignant, and occasionally disturbing, messages for a glimpse of the disembodied desires of others people's secret lives. Most people in relationships, however, would never make the giant leap of calling one of those numbers. Online, it's a whole different story. Driven by curiosity or boredom, people of every persuasion (gay, straight, old, young, married, single) visit the web's many millions of chatrooms, or browse the personals in online dating agencies, such as the hugely popular Australian agency, RSVP. According to RSVP marketing manager Melanie Bowman, the agency now boasts around 656,300 members, with hundreds more joining every day. For prospective flirts, it's a goldmine.

While Bowman admits that it's impossible to screen all applicants for Warnie-wannabes, through targeted marketing and the vigilance of its members - they're encouraged to report inappropriate behaviour such as lewd emails or cyber-stalking - RSVP has remained largely the domain of people who genuinely want to meet in person (the 900 weddings to date speak for its success). And the upside of cyber-flirting? The anonymity of this type of communication can create a "Dear Diary" style of intimacy. "People do get to know other people quite quickly," Bowman says, adding that, as a result, "They're more likely to tell someone their life story or their problems." The downside: a fast track to affair-ville.

When is an innocent bit of cyber chatter not so innocent? Email or SMS flirting between friends or workmates is rife and generally considered pretty harmless. Most people realise that the occasional flirty message isn't an invitation for a romantic tryst or a full-blown sexual affair; as part of a well-rounded friendship that includes face-to-face meeting and group interaction, a digital penpal poses no real threat to marital bonds. So how do people cross the line between that "xx" sign-off and XXX-rated communication?

Interestingly enough, the longer that two cyber-flirts put off having real-life interaction (assuming they've never met), the more damage the cyber affair can have on a marriage. "With email you have time to compose your thoughts. You can be much wittier, much more seductive," said one respondent in the Social Issues Research Centre's study. A relationship firmly rooted in cyberspace effectively becomes part therapy, and the resultant communication can take the place of real-world intimacy with a partner. The old "he/she just doesn't understand me" cliche becomes even more pronounced. Why? Well, put it this way: there are no chores, dirty dishes or toilet seats online. Just a whole lot of what many feel is neglected in their real-world relationships: communication.

Then there's the issue of internet-user profiles, which laud the user's best attributes and conceal the worst. Another relationship accelerant is the nature of cyber conversation. With less chance of embarrassment or public humiliation and a sense of physical safety, blatant questions ("What are you wearing/not wearing?") have become the hallmark of chatroom banter. The lower the chance of meeting, the more likely fantasy will be used to enliven conversation in place of the mundane truth. The result: an idealised person who can often seem far more articulate and compassionate than a real-life partner, and who never has to make good on their promises.

Even when cyber relationships don't work out, there's no need for a long, awkward dinner edging around the topic - it's as easy as blocking that person from emailing or texting you. Within minutes you can be having the same intimate dialogue with another virtual partner who can do no wrong. Unfortunately, cyber relationships are more likely to trigger obsession and addiction than real-life romances, says Melbourne counsellor, consultant and social commentator, Angela Lewis (MA Ed).

Even when there's no physical sexual relationship, the symptoms of an illicit cyber affair can be remarkably similar to falling in love in the real world (sweaty palms, shortness of breath, and an obsessive desire to hear from the lover). According to Dr Robert Friar, from Michigan's Ferris State University, specific chemicals are produced by the brain when we fall in love. "Phenylethylamine blocks our ability to see that person's flaws," he says. If the encounter leads to actual sexual activity at the keyboard, another ingredient in the brain's feelgood cocktail deals the final blow. "Oxytocin activates the brain's circuitry that causes bonding, whether you're sociologically or psychologically matched. It's released every time you have an orgasm," he says.

When confronted with cyber indiscretions (and, just like in the real world, affairs tend to be exposed eventually) many men and women claim that they weren't unfaithful because they never made physical contact. After all, they argue, if they've never even met, how is it any worse than fantasising about Brad Pitt or Angelina Jolie? Is sharing intimate emotional details with a stranger any different to talking to a close friend? Dr Monica Whitty, from Queen's University in Belfast, Northern Ireland, has become an expert on cyber psychology by asking exactly these kinds of questions. "When I embarked on the research, I wasn't sure whether online behaviour was going to be treated as acts of betrayal," she says. Soon a pattern emerged. "Cyber sex was the most problematic to a relationship. Having virtual sex in chatrooms was clearly an act of infidelity. Interestingly enough, conducting a non-sexual but emotionally intimate virtual relationship was almost as dangerous to a real-life relationship as an affair in person." Her findings aren't surprising. An earlier study found that most people whose partners had a sexual affair in person, recovered from the sexual trespass before they recovered from the fact that they were deceived. As with any kind of affair - physically consummated or not - sex isn't the only issue at stake.

For some men it's exactly the lack of sexual contact with cyber-flirting that's appealing. "It removes any possibility of performance anxiety, and other body insecurities," says Dr Whitty. "Some men find it easier to develop relationships this way. They feel enormous pressure to initiate contact with a woman and ask her out, but the thought of being humiliated turns them off. When rejected online, they don't have to see or talk to the person again."

Women are no different. With the anonymity of chatrooms, women can reconstruct their body image and shake off the taboos and social stigma dictating the sort of sex they should enjoy (in cyberspace, after all, no one can hear you moan).

Where men and women do differ, says Dr Whitty, "is in terms of sexual and emotional jealousy. It seems that women get more upset by emotional infidelity than men do."

And as far as initial motivation is concerned, he explains: "Some people are just sexually bored; others cheat because there's something wrong in their current relationship. When it comes to cyber affairs, it's easier to cut that off from the rest of your world. It's easy to find a partner online, too, easier than it is offline. As a consequence, I think there are potentially more affairs happening now."

So what's to be done? According to Dr Whitty, couples need to regularly discuss what's permitted in the relationship and what's not: "Mental fidelity is just as important as sexual fidelity." Interestingly, however, her studies also found that some couples believe their spouse having cyber sex stimulated their own sexual relationship.

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