WASHINGTON (AFP) - Two years ago, trapped in what he remembers as "a dead marriage", Michael logged on to adulterous dating site Ashley Madison for the first time. He was less than impressed.

"I was a regular for about three months," Michael, who works for a volunteer organisation in the Midwest, said on Tuesday (Aug 25) on condition of anonymity.

"Honestly, the site was terrible. Meeting real people was difficult. I'd wager most users, even paid ones, didn't even have anything close to an affair," he said.

"Many, like me, found it pointless and quit pretty soon after joining - but they didn't delete our information."

Today, he finds himself living in fear after his account details appeared - among those of 32 million others - in the most talked-about data hack of the year.

He worries not for his marriage - he and his wife have separated and divorce is in the works - but for the impact it could have on their child and on his job.

"My fear is that this will wreak havoc in all areas of my life. I have a good job, but many involved in it are religious. I could be fired," he said.

"What I did was wrong and I deeply regret it, but losing my job and putting my child at risk of poverty is hardly a fitting punishment."

"And I'm bothered by the smugness of the hackers and the glee of some on social media."

"Life is short. Have an affair" - so goes Ashley Madison's catchy slogan. But the impact of its data leak could have a long life.

It has triggered online extortion attempts and has been linked to at least two suicides, according to police in the Canadian city of Toronto, where the company is based.

The Pentagon is looking into Ashley Madison users who logged onto the site with military e-mail addresses. Adultery may be prosecuted in the US armed forces.

"It has left both families and unfaithful partners terrified, hopeless and even full of rage," psychology professor Nicolle Mayo at Mansfield University in Pennsylvania, told AFP.

Celebrity casualties include Josh Duggar, the 27-year-old star of a Christian family reality TV show who has blown nearly US$1,000 (S$1,401) on two Ashley Madison accounts since February 2013.

"I have been the biggest hypocrite," Duggar, who earlier this year acknowledged involvement in sexual misconduct in his teen years, confessed in a statement.

Ashley Madison's parent company Avid Life Media is offering a C$500,000 (S$527,735) reward for information leading to the arrest of the hackers, who brand themselves the "Impact Team".

Avid Life Media in turn is being sued by a disabled Canadian widower who says he joined Ashley Madison "in search of companionship" after losing his wife of 30 years to breast cancer.

Ms Joslin Davis, president-elect of the American Academy of Matrimonial Lawyers, said there has been "no measurable uptick" in the number of calls to family lawyers prompted by the Ashley Madison hack.

But in the offices of Internet reputation and public relations consultants, phones have been ringing off the hook.

"It's a mixed bag of people - all men, shockingly," said Ms Courtney Fitzpatrick, media director of Status Labs, which has been contacted by about 50 Ashley Madison clients so far.

"Some of them are claiming identity theft; some are admitted cheaters but very sorry for what they did," she told AFP.

"Others are blatant cheaters and afraid of being caught by their wives."

Dr Denise Friedman, chair of the psychology department at Roanoke College in Virginia, said Ashley Madison users are learning the hard way that nothing in cyberspace is ever genuinely private.

"You put stuff online and it doesn't matter how secure you think it is" because someone is always liable to crack the firewalls that supposedly protect it, said Dr Friedman, who studies the impact of social media on relationships.