In the minds of most people, she was the most famous gold digger in America, which explains the cataclysmic jolt to the daily news cycle, the explosion of office babble, the reiteration of a joke that went pretty much like this: "And will you always remember where you were when you heard that Anna Nicole Smith died?" For as much as she was a figure of fun, a goddess of tabloid abundance, the shock of her death at 39 was far bigger than that of just any celebrity. She had gotten under our skin, and taken on a role we didn't quite realize was so big in the history of marriage, money and sex.

Poor Anna began her climb to fame and riches as a stripper, and in the end, she was a stripper again, seemingly uncontainable by ordinary clothing. She spilled out of her tops, she spilled into the tabloids, she was a mess. Her death gave you whiplash: Time to feel sad for a woman who was never supposed to be more than a source of amusement. Her final notice was never intended for the front page, just a few inches, 40 years hence, at the back of the obits, reminding us of the bombshell who married well . . . and was forgotten as her beauty faded.

"Courtesan," which in a different age is probably what she would have been labeled (even though she was married), is a category we don't have much use for anymore. The woman who makes sexual alliances for money, who was less than a blushing bride but not so fallen as a prostitute, was once a vigorous cultural type, at least through the 19th century. Courtesans were the essential heroines of our greatest operas. They offered up their bodies, in various states of undress, to painters from Caravaggio to Toulouse-Lautrec -- and too many others to mention. It was a courtesan who set in motion many of our greatest novels, not least of them Proust's "Remembrance of Things Past" -- which begins with the love of a man named Swann for a "great courtesan."

But the idea of the courtesan has all but disappeared, and with it much of the nuance about our analysis of sex and marriage.

Our continuum of sexual alliances runs from the happy marriage of loving equals, on one end, to prostitution -- the pure exchange of sex for money -- on the other. The trophy bride, the marriage of youth and beauty to age and power, is the closest we have to the category of the courtesan -- but it involves the collective pretense that it isn't only about money. To see the old category of courtesanship in operation today, you have to travel to poor places around the globe, where sex, love and sometimes marriages are negotiated between wealthy westerners and local girls without either party acknowledging the idea that the exchange is commercial.

The courtesan was rich but not on her own terms, an object of scorn but not completely disreputable, a living reminder of an economy of sexual exchange that we like to pretend doesn't exist. When Anna Nicole Smith, a voluptuous 26-year-old Playboy Playmate, married an octogenarian oil-rich billionaire, she crossed a line, assuming too high a place in our supposedly mobile society. After her elderly husband died a little over a year later, she stood to inherit $474 million (still in legal dispute), and her name became shorthand for marital opportunism. Her husband went down in the books as the most ridiculous of old goats -- but he was dead and beyond the reach of our scorn. Anna had her second and third acts, on television and shilling for diet pills, but none of these chapters ever did much for her dignity.

Society took its revenge, confining her to gossip magazines and scandal sheets, foreclosing her appearance in the black-and-white party photos of respectable magazines, where trophy brides appear smiling and dazzling with their balding, sagging, tremendously rich husbands.

For centuries, there have been men who have wondered why women really love them. That the real sexual allure of men may not be their good looks, their masculinity or their charm, but rather their power and position, can make men wonder whether they are loved for themselves or for something external and unrelated. When marriages don't look like they look in storybooks -- love matches between princes and princesses -- intimacy is shadowed with doubt.

And it's the same fear that made poor Anna Nicole Smith gibes an endlessly rich source of material for Leno and Letterman; they were laughing at her, of course, but also at men who were foolish enough to marry women like her. We laugh at what makes us uncomfortable, and Anna Nicole Smith made us very uncomfortable indeed.

In the post-feminist age, there has been some gradual reemergence of ideas about love and marriage that are not based on equality or sameness between the sexes. Women are different than men, the argument goes. They look for security and safety, while men look for sexual novelty and opportunity. Men, as Newt Gingrich once said in his famous "giraffe hunting" explanation of biological difference, "are basically little piglets."

Marriage, the thinking goes in some conservative quarters, is about combining the little piglets with the other half of the equation, the women who naturally seek shelter in a hostile world. These alliances are essential for the propagation of the species, the perpetuation of the family. Loveless marriages are a fact of life, but not nearly so dangerous as divorces born of selfishness. Yet the woman who is hard-nosed in her pursuit of the biggest little piglet she can find becomes an object of scorn.

It's difficult to believe in such a mechanistic model of marriage -- two biological entities with very different agendas, looking for the best deal they can find -- without bringing back a lot of cynicism about marriage. That cynicism is nothing new. The 19th century had a far more trenchant view of the very contractual nature of most marriages. Tolstoy, in his novella "The Kreutzer Sonata," condemned marriage wholesale, as a societally sanctioned form of sexual servitude. In "Dombey and Son," Dickens analyzed the marriage of a beautiful, accomplished, independent woman who marries (at about the last moment before she will no longer be sexually marketable) a man of great wealth and no personal charm. To the outside world it seems a brilliant marriage, an alliance of grace and beauty with wealth and power. But she has contempt not just for her husband, but for herself and the whole system of marriage. That contempt cleaves her soul.

We never really knew what motivated Anna Nicole Smith's marriage. Perhaps it wasn't so crass and calculating as it seemed from the outside. But she was clearly unhappy. Now she seems merely a sad and pathetic creature, rather like her forebears in the world of courtesans, Manon (Abbe Prevost's doomed courtesan) and Violetta (Verdi's hooker with a heart of gold) and Proust's Odette. We are at the end of the opera, the wandering woman is dead, and now the clown is the victim. Neither category really does her justice, and so the false tears and moral clucking will sound together -- a reminder that we have eliminated yet another sexual category that allowed for contradiction and ambiguity.