That may sound like a cautionary tale, but for Noel Biderman and others who have founded dating websites for married people, it's a lucrative business.

"The day after Valentine's Day is one of our biggest days of the year," says Biderman, founder and CEO of Ashley Madison, a 10-year-old site that unapologetically caters to "discreet" encounters for the married or otherwise attached. "People are disappointed by their spouses' lack of effort, and they feel especially undervalued when there is a societal expectation of romance. Certain days of the year act as litmus tests for many people in relationships."

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Websites designed to facilitate cheating appear to be thriving; some earn tens of millions of dollars a year, and competition is growing. In addition to Toronto-based Ashley Madison, there's a growing crop of copycats that equate affairs with romance, passion and adventure.

Whether these sites promote cheating or just facilitate it is up for debate.

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Stephania Meyer, 40, and her husband Michael Oshust, 43 met online on Ashley Madison, a dating website for the married and attached. Meyer was married and Oshust was still married but getting a divorce. The couple married Feb. 15, 2007.

"People are going to cheat regardless of whether Ashley Madison is there or not," says sociologist Diane Kholos Wysocki of the University of Nebraska-Kearney, who has surveyed the site's members for her latest research. "There's a bigger social issue going on — people aren't taking care of their marriages.

"It's not so much that they're going to these cheating websites because the sex is greater or the person is more beautiful. It's because the person is giving them attention they're not getting at home."

Some of the sites are based in Europe and increasingly have become international, with their eye on the USA.

"American people are really hypocrites about infidelity," says Teddy Truchot, co-founder of Gleeden, which launched in Europe in 2009, moved into Australia and entered the U.S. market last fall. Its headquarters are in New York, and it plans to start an ad campaign here March 1.

"Everything from the U.S. which comes to Europe is about infidelity," says Truchot, 29, who moved to Los Angeles two years ago from Paris. "You see cheating all over TV and in real life. … Everyone is cheating here."

Those who study infidelity disagree. Data from 2010 from the General Social Survey, a sociological survey of 1,303 adults considered among the most reliable for infidelity statistics, show that 19% of men and 14% of women reported ever having had an extramarital partner.

But the experts acknowledge that it is easier to have a liaison today. They say that when celebrities and politicians are repeatedly caught cheating — even on their stunning spouses — it begins to normalize the behavior. Also, business travel and telecommuting sometimes make the logistics of an affair less unwieldy. And the Internet and personal devices mean there can be direct communication with a paramour (or check-in with a spouse) anytime.

"The big surprise to couples is they assume they're going to have a monogamous marriage and don't really talk about what are the expectations and what are the vulnerabilities," says sex therapist and clinical psychologist Barry McCarthy, a professor of psychology at American University in Washington, D.C.

Kholos Wysocki, who since 1992 has studied Internet relationships, sexting and cybersex, says her latest analysis looks at 5,187 adults who took her survey when visiting Ashley Madison during three months it was posted in 2010. Though she acknowledges this kind of survey has limitations, she says 68% of men and 61% of women reported cheating, either physically or virtually, while in a serious relationship.

Stephania Meyer, 40, of Newmarket, Ontario, says her 11th wedding anniversary was approaching in 2004 when a radio commercial about Ashley Madison caught her attention. She was a stay-at-home mom of two, in a marriage she says wasn't working. "We had grown apart. We tried counseling and vacations alone to try to rekindle the relationship and get that spark back, but it just wasn't there," she says. "We just got married really young, and the only thing we had in common were the kids."

Meyer says the ad got her thinking "maybe there was someone out there I could actually talk with. I wasn't looking to hook up with someone for a one-night stand. I was lonely in my marriage. I wasn't thinking long-term. I didn't want to hurt my family. I was just thinking of me at the time, and because their promotions are all about the discreetness of it, I felt no one was ever going to know."

Michael Oshust, 43, was in the midst of a divorce and living apart from his wife in Oakville, Ontario, when he heard a similar radio ad. Being discreet appealed to him. "The person inside of me said, 'I am still married.' I just felt I'm still married."

So Oshust, an IT project manager, created a profile on the site. He contacted women but says he never physically met anyone until Meyer.

Neither had posted a photo, which isn't unusual for such sites. They started messaging through the website but later used e-mail and the phone, and they exchanged photos. About five weeks later, they met at a coffee shop in a nearby town and ended up in a hotel room. Just before Christmas, Meyer's husband discovered her e-mails and kicked her out. Within weeks, Oshust moved to Newmarket and the couple moved in together. They married five years ago.

Affairs as marriage savers?

Ashley Madison yesterday marked its 10th anniversary. Ever since Biderman, 40, of Toronto founded the site (slogan: "Life is short. Have an affair.") he has been blamed for promoting infidelity. But he says he's saving marriages — he calls an affair a "marriage preservation device" that his website facilitates.

"People do cheat on their partners," says Biderman, who has been married "eight perfect, wonderful years" and has two kids, ages 7 and 4.

"It doesn't mean they don't love them or don't want to stay married to them. Marriage is about more than sex. An affair, and my service in particular, makes them happier to sustain their lives within the marriage construct."

He says he wouldn't cheat on his wife, Amanda, 37, and she agrees. "We wouldn't do it to each other, but we can't judge how somebody wants to live their lives," she says.

Ashley Madison (named for two top girls' names when the site was being created) earns well over $60 million a year, suggests online dating industry analyst Mark Brooks.

Biderman says that estimate is "on target," but he's expecting greater revenue this year. "I think I'm seeing $100 million a year right in front of us," he says. The company has 120 employees in Toronto and one each in Milan, Madrid, Berlin, Dublin, Sao Paolo and Mexico City.

Biderman is not worried about other startups — which he calls "impostors" — encroaching on his market; his "true competitors" are Facebook and the workplace, he says.

He got the idea for his site as a sports attorney, helping former NBA athletes find other countries in which to extend their careers. "It felt to me 99% of my clients were unfaithful. I spent half my time dealing with domestic issues."

An article he read about dating websites made him realize "there was a whole other marketplace" waiting to be tapped: "people in relationships who want something on the side."

"Maybe I had to be a sports agent living in the world of unfaithfulness" to make the connection, he adds.

Amanda Biderman, who used to work in marketing and does some consulting, says their research found that single women looking for love were often victims of married men using singles dating sites to cheat on their wives.

"It was a market gap and an issue that needed to be addressed. That's how I see it," she says. "I try to focus more on that it's a business … giving people what they need.

"In a way, the business has only helped me in learning how to be a happy couple. It's easy to say you don't feel like having sex or you're tired or whatever. I make a real effort. If Noel wants be intimate, I can change my mind-set instead of just saying 'tomorrow.' "

The experts don't agree

Psychologists and relationship experts don't buy the theory that cheating can save a marriage.

Researcher John Gottman, an emeritus professor of psychology at the University of Washington in Seattle, calls sites such as Biderman's "destructive."

"I don't think he's saving marriages at all. I think he's ruining marriages," Gottman says.

Sex educator Logan Levkoff of New York, author of How to Get Your Wife to Have Sex With You, agrees. "This deliberate betrayal is so disrespectful," she says. "It's the easy way out instead of doing the tough work to repair what's making you unhappy in your sex life, in your relationship.

"This idea that you can sneak around and still have this wonderful life is really problematic. Where is the personal accountability? Where is the respect for your relationship? Not every couple is meant to stay together, but ideally, you exit a relationship with the same respect as you entered into one."

Many cheating websites — industry tracker Brooks counts well over 30 — promote the hush-hush nature of the business, which he says still doesn't disguise the objective.

Brooks, of Sliema, on the island of Malta, is quick to disclose that he has been a paid consultant for many online dating services, including those he calls "philanderer sites."

"The philandering sites are specific to people who are wanting to be discreet," he says.

"As much as I abhor these sites, they do actually do something good for the industry. People can be who they are on the philanderer sites," he says, rather than have married people claiming to be single, which happens on singles dating sites, he says.

Other adult dating sites may suggest they're "discreet," but Brooks says he draws the line between the cheating sites like Ashley Madison and others by the photos. Adult dating sites such as Lonely Cheating Wives, Affairs Club, Married and Lonely People, Married Date Link and Discreet Adventures, among others, are "risqué photographs, anything goes, sexual preferences disclosed."

Biderman says it took five years to get the first 1 million anonymous members, but the total who have ever registered and created a free profile is 12.6 million. Currently, just over 2.3 million are registered and considered active by logging in or taking an action within the past 30 days (97% who log in take an action, he says). Members pay to communicate, $49 for 100 credits. Credits are used to send an e-mail, to chat in real time, or to send a virtual "gift," such as a rose, necklace or Champagne bottle, Biderman says.

About 70% of registered members are men, but Biderman says that in certain cities, the percentage of women is higher, such as Rio de Janeiro (44%) and Houston (37%).

Biderman says all communication on his site is encrypted, but he can't protect people who are sloppy with their devices.

Divorce attorney Kathryn Dickerson of Tysons Corner, Va., says websites can erase and delete all they want, but "they have no control over the cheating spouse's computer."

"It's gotten so much harder to keep things secret," Dickerson says, noting that people who suspect a spouse of cheating can install devices that capture keystrokes, do screen grabs and keep a record without the user knowing.

Data from the online market research firm ComScore show that AshleyMadison.com had 557,000 unique visitors in December 2011, up from 487,000 in December 2010. But for most of 2011, ComScore shows its monthly unique visitors at 700,000 to 800,000. Biderman says those numbers are "greatly underreported" and his unique visitor count captured by Google Analytics for December was 8.6 million. He also says December traffic is lower because of family holiday obligations.

Brooks says he's surprised that in 10 years, Biderman's site hasn't had a lot of direct competition. Part of it, he says, is that "people don't like to start that kind of business."

But Gleeden is ready to take that on.

Ashley Madison's image is "too sexy," Truchot says in a thick French accent.

"We are European, and we're trying to be more classy."