There’s a chilling (to me) moment in Sex: The Annabel Chong Story, a recent documentary about the porn star who made history by having 251 acts of penile penetration in a span of 10 hours: Chong says that she was aware of the risk of HIV, but that “good sex is worth dying for.” Apparently another porn star felt the same way, only more so, and bested Chong by 369 boffs.

In July, itching to outdo both scores and make a bundle in the process, porn impresario Forest Williams offers “amateur” women the chance to make it 621 times, break the record and take home a cool million at an event he dubbed “Who Wants to Shag to Be a Millionaire?” (Suposedly, a cut of the proceeds is to go to local AIDS organizations, though by as late as September no specifics have emerged.)

The location of this competitive gang-bang is San Francisco’s Power Exchange, a gay sex club. I arrive at 1 p.m., an hour into the sex-a-thon. To make the site extra heterosexy, posters advertising porn have been hung. I’m fascinated by one of a Goth chick marrying a skeleton. Freudian slip, anyone?

There are three “sets” where the action takes place, each with a bed with black rubber sheets and -- what a relief! -- safe-sex supplies. At least I won’t be witnessing wild HIV risk-taking. Of course, even with condoms, there’s always HPV or crabs.

“Should I double-bag it?” asks a hairy, paunchy, naked middle-aged man eager to go first. It’s hard to tell who he’s asking -- contestant No. 1, Libra, a perky blond swinger, or her husband, who’s busy filling small paper condiment cups with lube. They decide on one condom. It’s reassuring to see three heterosexuals calmly negotiating safe sex, whatever the circumstances.

And they’re off! Just before the two-minute time limit per man, Libra’s first partner has a very raucous orgasm. The photographers go nuts. It’s embarrassing to watch their sharklike swarming during his “moment.”

Contestant No. 2, who goes by the handle Hot Chocolate and is wearing a “Sex Kitten” tank top, also has a male assistant, her boyfriend. A petite African American with beautiful braids, she’s obviously disappointed with the low turnout. Despite a plug on Howard Stern’s morning show, only a few dozen guys have thrown down $50 each to help make sex history. But the rules say consecutive partners can include repeat “visitors.” Crows one happy camper dialing his cell phone: "Man, they said call your friends, so I am!"

The third woman, Raini, is a forty-something blond waitress -- and a bit scary. She breaks the one-guy-at-a-time and no-blowjobs rules. To my mind, the sexiest person around is Raini’s chaperone, who doubles as “the fluffer,” giving the guys a literal helping hand to get it and keep it up. During a pause in the action, she whips up a storm of sexual energy by mounting each contestant while wearing her own impressive strap-on over a purple lace body-stocking.

That’s about when Mitch Katz, MD, director of the city’s Department of Public Health, makes a discreet pass-through. The bright lighting makes the condoms gleam for his inspection as he chats softly and amiably with one of the club owners. It’s a classic San Francisco “the personal is political” moment.

I take a break -- eyeballing nonstop copulation is exhausting -- and come back just after 10 p.m. only to discover that the show’s already over. Nobody got even close to Chong’s ch-ching! due to too-few comers, a cigarette-smoking techie tells me, but Raini enjoyed a kind of triumph by outlasting her competitors. It’s all, well, anticlimactic. Yeah, I’ve got a great story to tell about the wild things I’ve seen. But I can’t even begin to imagine what the contestants got in return.