For the Thrill of the Affair: Why Married Women Cheat

April 17, 2014— -- When women cheat, it’s often considered a scandal, and never has cheating been as easy as it is now, when finding a willing partner is a click or a phone tap away.

But what drives women to cheat? And do they stray as much and for the same reasons as men?

Katherine, whose name has been changed, said she and her husband were married for 14 years. After undergoing major weight loss and multiple plastic surgeries, she began looking for excitement outside of what she said was a stale marriage and turned to AshleyMadison.com, the notorious dating website for “casual encounters.”

“I was feeling very lonely one night,” Katherine said. “I was bored, on my phone in the parking lot, sitting in my car, pulled up AshleyMadison, and decided to open my first profile to see what would happen.”

AshleyMadison.com’s motto is “life is short, have an affair.” Noel Biderman, the author of "Adultropology: The Cyber-Anthropology Behind Infidelity," started the site more than 10 years ago. He said he makes more than $40 million a month from it.

“We’re the second-biggest dating service on the planet,” Biderman said. “This is not a kid’s game. This is an enterprise of significance.”

Biderman and his wife Amanda Biderman, who rarely gives interviews, agreed to sit down with “Nightline” to discuss his website and their marriage. She said when he first told her about the idea for the site, she was leery.

“I wanted to make sure he wasn’t having a mid-life crisis,” Amanda Biderman said. “Then I got to understand it more and thought it was interesting.”

Noel Biderman said he has built a billion-dollar business betting on infidelity, and now has 25 million members in 37 countries, but doesn’t believe he is encouraging people to cheat, just providing one outlet.

“Long before I launched AshleyMadison there were affairs, and long after I’m gone there will be affairs,” Biderman said. “What I’m trying to do is help people have the more perfect affair.”

“I’m encouraging secrecy, yes,” he added, “but I’m not necessarily encouraging infidelity. I don’t think it needs all that much encouragement.”

Wendy Plump knows all about the elusive allure of an affair: keeping secrets. She said she strayed with three different men during her 18-year marriage.

“It is like a drug, a rush,” Plump said. “You know what it’s like when you fall in love with someone or your spouse? It’s like that when you have an affair, all over again.”

But it turned out that she wasn’t the only one in her marriage who was cheating. The final betrayal, she said, was discovering her husband had fathered a child with his long-term mistress.

“I remember having everything crash in at the time,” Plump said. “Something incomprehensible as to how you could get around that. ... I don't want to make it seem like he was terrible and I was good because we both let the marriage down.”

Plump, a veteran reporter, turned her failed marriage into the subject of her memoir, “The Vow.” She and her husband are now divorced.

“I got many letter from women who had affairs or whose husbands had had affairs,” she said. “This is a lot more common than I would have imagined.”

Some statistics show that 21 percent of married men have had an affair, compared to 15 percent of married woman, according to the National Opinion Research Center's General Social Survey. But that number for women has spiked in the last two decades, up nearly 40 percent.

Plump said society still judges cheating wives much more harshly than cheating husbands.