ON any given night in Sydney, lipsticks fly, curling wands sizzle and aftershave slathers as men and women across the city prime themselves for a date with someone who may be, but probably isn't, the one.

What they know, but might surprise those outside the dating scene, is that the lipstick isn't just for decoration; it's war paint. The barstools are ramparts, the boutique beers are shields and the fake eyelashes and waxed chests are weapons in an increasingly hostile battle between two opposing armies that are supposed to be falling in love with each other.

"What's happening out there is a disaster," says Yvonne Allen, who founded Australia's oldest introduction agency in 1976. "There's an alienation happening between the sexes."

The front line is the 30-45 age group, which makes up 50 per cent of those signed on to dating site RSVP. Unlike 20-somethings who are in no rush, or the 45-pluses looking for companionship, these men and women are at the business end of dating, most likely to be looking for a husband/wife and father/mother for their unborn children.

But feel for them - their dating environment is different to any that has gone before. There's a lot at stake but instead of bringing them together, the pressure is tearing them apart.

Women say their trust has been eroded by playboys lying about their intentions, married men pretending to be single, or men who are creepy or threatening. They meet men who date without ethics, who text but never call, who just stop communicating rather than say they're no longer interested, or who juggle lots of women at once.

But men say they are sick of women who only seem interested in how much money they earn, who are "sperm hunters" (as one man put it), panicked by their biological clock, or who have a fussy shopping list, insisting they'll only marry a tall banker who rows and builds his own furniture, and refusing to even consider a renter. They say women judge them on their clothes, their car, or their job, not on whether they'd be loving husbands or enthusiastic fathers.

"Sydney is cold and harsh, people are quite critical," says Trudy Gilbert, who runs Elite Introductions. "Sydney daters probably have a bit of a tougher check list than people in other cities do."Women have more choices than ever. They are earning high wages, buying their own properties and they are well aware they don't have to stay in bad relationships. They have worked hard and done well, and, understandably, are looking for men who have done the same. As a result, they are putting off marriage - some through choice, some through fussiness, others because a relationship they thought would end in marriage and children failed.

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But public education campaigns and women's magazines are alerting women to the fact that while they may have no limit to their career, their window of opportunity for having children is finite. So loud are these messages that it has created a panic among some (not all) 30-pluses.

It's at this age that the numbers game, which favoured women throughout their 20s, starts to tip towards men. Social analyst Mark McCrindle says there are more men than women until age 33, when the ratio is the same. From then, there is, as some have put it, a "man drought" where, unless you live in the Northern Territory or parts of WA, there are more women in your age group than men, a problem worsened by the fact that men, on average, marry women who are two years younger than them.

Suddenly, market forces favour the bloke. And he's resentful that women, who ignored him when they were in their 20s, are suddenly showing interest, says dating coach Bettina Arndt. "Some of those guys are very bitter," she says. "One I spoke to was just determined to play the field. It's almost a vengeance thing, having been dismissed by women for so many years."

On top of this dangerous dating mix comes the most fundamental change to romance in centuries: online dating.

Sociologists have poured a wealth of research funding into investigating this phenomenon and have decided that while internet dating has fundamentally changed romance as we know it, it has not necessarily been for the better.

In some respects, internet dating is a godsend, particularly for those whose friends are married and whose options for meeting people have dried up.

"It has that innate ice-breaking context where everyone has their cards out, saying I'm here to meet someone," said one dater.

But internet dating is also traditional courtship in reverse. Usually two people strike up a conversation, decide whether they feel comfortable, then gradually get to know each other. On the internet, they find out a wealth of information before a face-to-face reality check. It can also lead to a shopping-list mentality.

"The ruthless summation of people into brackets based on career, education and appearance turns relationships into a commodity based on what you think you're entitled to," says one former dater. "More often than not you'll end up with someone pretending to be the person you've fooled yourself into thinking you want - and that's a recipe for disaster."

Lying is also a common hazard (although that happens offline as well), especially as screen names can free people from social norms.

Studies show that about 20 per cent of daters admit to deception but think 90 per cent of other people are lying. Women tend to lie about weight, while men are more likely to fudge education, income, height, age and marital status (one study found 13 per cent of men dating online are married).

Another issue is the sheer range of options. If one date doesn't work out, chances are there's another email waiting in the inbox - a conveyer belt of potential dates encouraging extreme fussiness and a lack of effort.

"(It) can elicit an evaluative, assessment-oriented mindset that leads online daters to objectify potential partners and might even undermine their willingness to commit to one of them," says a US psychological study into online dating. "It can also cause people to make lazy, ill-advised decisions when selecting among the large array of potential partners."

Unlike a meeting set up by a friend, or an old-fashioned matchmaker, there's no accountability on dating websites. "Some of the people on those sites are misleading and deceptive, they're not what they say they are," says one online dater and lawyer.

"If this was a product, you'd have the Australian Competition and Consumer Commission shutting it down for false conduct because what's on there doesn't match what it claims to be."

Many might complain about the lucky dip that's online dating but singles keep coming back to it because it works. There may be tens of thousands of horror stories (See Inside Edition, page 37) but also many weddings.

Then there's the changing sexual mores. For women in their mid-30s, Brazilian waxes, sexting and some more adventurous aspects that have bled into mainstream from the pornified sexual culture of 20-somethings comes as an often unpleasant surprise. But it's a culture that has been embraced by the 30 and 40-something men they're dating.

The ever-changing roles of men and women in our society have collided with online dating without a code of conduct to make it all work properly. There are no longer any accepted rules of behaviour to govern romance.

This affects the big things - if a woman discovers the man she is dating has lied about seeing other women, she can't hold him to account in front of his friends. It also confuses the little things. One man might want a woman to pay her way, while another would be offended at the thought. Is asking for a date the next day too forward? Is texting rather than calling too lazy?

How can daters signal their intentions or interpret the intentions in this age where anything goes? The litany of bad experiences on both sides creates then widens a chasm between men and women in this city. And so the mating ritual becomes a war dance, and the casualties are romance and trust.