There are signs that, as in so many areas of modern life, standards of infidelity are in decline. An American congressman called Anthony Weiner has admitted taking photographs of his crotch and sending them to women he had never met.
Here it has been reported that Ryan Giggs had an affair with his sister-in-law, which resulted in an abortion.
No wonder there is such a resurgence of interest in Betrayal, Harold Pinter's famous play from the golden age of adultery, the 1960s, based on his equally famous affair with Joan Bakewell.
For the seven years they were seeing each other -- in the biblical sense -- both were glamorous public figures, yet they kept their love out of the public gaze.
When eventually some of their friends realised what was going on, they took a grown-up approach and kept a discreet silence.
"There was something different about life then," Bakewell wrote at the weekend. "People had a sense of the right to privacy ... It was assumed that affairs arose from the dynamic of human relations - - the unavoidable attraction of more than one person in one's life - - and were viewed benignly until people began to get hurt."
Since those days, infidelity has rather gone off the rails. It may be that, away from priapic footballers and weinering politicians, some honourable affairs, passionate and sad, are taking place.
But Bakewell is right: the attitude which surrounds the love life of others has changed. The sense of sympathy, the awareness that, even in the best-ordered lives, people can fall in love with the wrong person at the wrong time, has faded.
The modern view is prim and unforgiving. We are fascinated by the sex lives of others but, even as we ogle, we tend to take a position of bogus moral superiority. A man who messes up his marriage by falling in love with another woman is, it is unquestioningly assumed, a rat of misbehaviour who should forever be distrusted.
The career of Robin Cook never quite recovered from the way his marriage ended and that of Chris Huhne may be heading in the same direction.
The betrayed wife is offered an unattractive choice: she can make a career out of her victimhood, writing about the awfulness of men in public life every time a new scandal appears, or she can refuse to rage and exact revenge, in which case she is likely to be treated with particular contempt.
Even when public marriages come to an end in an apparently civilised fashion, as in the recent case of Trevor Nunn and Imogen Stubbs, the public view of them is sceptical, faintly incredulous. Some might argue that we have become more sensitive in recent decades; that we understand the pain and hurt which betrayal can cause and are no longer prepared to accept it.
With this new moral vigilantism, a Pinter-Bakewell affair would have not the slightest chance of remaining private. A conscientious friend would feel obliged to have a quiet word with a journalist whose paper, again with the most elevated motives, would run a campaign of disapproving revelation.
These are the morals of a Victorian novelette. Any kind of human muddle involving the competing demands of love, desire, loyalty, fear and daring is reduced to the level of villain, or victim.
Yet what a shallow, priggish view of love these assumptions represent. How absurd it is to believe that, to be decent and honourable, a person should always live and love according to the same unbending precepts.
As Pinter -- like all great writers -- knew, there is often something true, tragic and noble in betrayal.