Oh, my.

How on Earth does one go about judging the value of a movie like A Dirty Shame, the latest NC-17-rated sex farce from John Waters?

My normal standards of evaluation tend to crumble when the movie in question includes characters with names like Loose Linda and makes use of the phrase "Let's go sexin' " upwards of three times.

It's not porn; not even close. Despite the prominence it affords nudity, groping and masturbation, A Dirty Shame amazingly doesn't include anything that could technically be considered a sex scene. And yet still, it is quite possibly the most sex-centric movie I've ever seen, and that's including porn, er, what I've heard about porn.

The absurdly simple plot follows the transformation of Sylvia Stickles (Tracey Ullman) from an icy homemaker to a red-hot sex fiend following a concussion to the head. Guiding her along on her path to sexual enlightenment are a sex sage named Ray-Ray (Johnny Knoxville) and his 11 "apostles" who each boast a different carnal perversion. One of them, Caprice (Selma Blair), also happens to be Sylvia's teenaged daughter.

Sylvia, whom Ray-Ray alleges to be the prophesied 12th apostle, is destined to bring to the world a brand new sexual act. In order to do so, however, she must first stop the "neuters," a group of conservative townspeople who are trying to stop the sudden wave of sexual deviance that has spread to several people in the town. Spearheading the group are Sylvia's repressive mother Ethel (Suzanne Shepherd) and her aww-shucksey husband, Vaughn (Chris Isaak).

The rest of the movie is a continuation of this basic premise and, as you might have guessed, by the 30th or so time that ordinary Baltimore townsfolk burst out into spontaneous acts of prurience, the joke does get kind of old.

Although A Dirty Shame is basically tight (stop giggling) in just about every way, some barely tangible element of it just doesn't quite work for me. Maybe it's that although all the characters are reduced to caricatures and the situations totally absurd there still isn't very much humor in the movie -- excepting the delightfully racy soundtrack and a couple of the funniest puns I've heard since middle school.

Or maybe it's that Waters' attempts to tear down religion in A Dirty Shame feel more like he's just blindly poking fun than calculatedly satirizing.

Or maybe it's the film's stubbornly simplistic worldview, where every possible negative consequence of sex is completely ignored or glossed over -- at one point, one of the apostles thanks Ray-Ray for curing him of syphilis, but doesn't elaborate at all.

This is somewhat moot, I realize, because Waters' fan base won't be swayed away from seeing it, nor will his vehement detractors ever be persuaded that there is any value in his work.

As for those who have not yet seen any of Waters' repertoire, I'll describe his appeal thusly: If your favorite moment of the South Park movie was the musical number with the title we aren't allowed to print, then you'd probably dig his work, of which A Dirty Shame is indicative.