USA TODAY - Feb 14 - 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 AshleyMadison (AM). 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. "Everything from the U.S. which comes to Europe is about infidelity," says Truchot. "You see cheating all over TV and in real life." Data from 2010 from the General Social Survey shows that 19% of men and 14% of women reported ever having had an extramarital partner. AM earns well over $60M a year, suggests online dating industry analyst Mark Brooks. Biderman says that estimate is "on target," but he's expecting greater revenue this year ($100M). Industry tracker Brooks counts well over 30 cheating websites. He 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. Biderman says it took five years to get the first 1M anonymous members. Currently, ~2.3M are registered and considered active by logging in or taking an action within the past 30 days. 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.