I hate acting a pedant, but the reporting around the Ashley Madison hacking has me chafing over word choices. Over and over, news reports have described Ashley Madison as a "cheating" website, an online community for "cheaters" to meet one another. I understand the historical use of the term "cheater" to describe someone who has sex with a person other than his or her romantic partner and "cheating" as the actual sexy-time that transpires with someone other than their romantic partner, but I still think the terminology is bullshit.
To cheat is to gain an unfair advantage in a competition, but romantic relationships aren't a game. My marriage isn't a competition. I don't have to lose for my wife to win, and vice versa. Even when you pull off the 'till death do we part' thing, here's no prize at the end of your relationship; the relationship is the prize in and of itself. Tom Brady can cheat at football to gain an unfair advantage over his team's opponents, but I can't "cheat" at my marriage because there's no opponent for me to get an unfair advantage over. Relationships aren't a zero-sum game.
I don't doubt for a second that many of the now exposed Ashley Madison users are jerks. Likely many are lousy romantic partners. Many of them have probably been dishonest with their partner--although you shouldn't assume that dishonesty is intrinsic in every affair. Many of them may even cheat at checkers or cards, but they aren't cheating in their marriage.
I daresay that the mindset of marriage as a zero-sum competition wrecks more marriage than affairs. There are plenty of good reasons, along with numerous bad ones, to aspire to monogamy. Failing at an aspiration to monogamy, even intentionally failing by putting an ad on the internet, may damage a relationship, but it isn't one person winning the relationship at another's expense. Worrying about who's 'winning' the relationship seems like a pretty sure way for everyone involved to lose.
Cheaters may never win, but nobody can win a marriage.