To the devil's advocate who made the divorce court comment:
It wouldn't PROVE that someone has been, or is cheating. It only reveals that people have been talking about it. Why? Because CONTEXT can't be proven, only CONTENT. A person (or both persons involved) could simply say it was a fantasy, or an inside joke, and the courts would have to weigh that.
It absolutely doesn't prove infidelity. I know, because I watched a company incapable of firing two employees engaged in an extramarital affair in the work place (in an office, no less, which is why they were being terminated) because they claimed the email exchanges were simply a joke. No matter how vulgar, descriptive, and real it sounds, people can simply deny context and get away with it.
Eventually, the employer just had to deem their discussions work-inappropriate to enforce disciplinary action, but they were unable to terminate their employment because of arbitration defense from a union rep. In a court of law (dealing with divorce), a good defense attorney will chew up the "text proves infidelity" case.