How a Scandalous Sex Site Stays Hot in the Era of Throuples

Ah, the scandalous 2010s: Anthony Weiner’s sexts, Fifty Shades of Grey, Arnold Schwarzenegger’s love child. It was in this fecund soil that Ashley Madison—the infamous website dedicated to extramarital affairs—became a household name. The website and its purposely eye-raising slogan—“Life is short, have an affair”—seemed to define a decade filled with tawdry turpitude and tabloid titillation.

But when I recently received an email from the Ashley Madison press team...