As a photographer who sometimes takes pictures of pretty girls doing "open" poses, and as a person with an M.A. in philosophy and lots of interest in aesthetics and ethics, I am perhaps uniquely qualified to discuss this topic in a serious manner.
That said, I want to consider two main questions: 1) Do open poses oppress women? and 2) When are open poses pornographic and when are they erotic?

Before addressing these issues, let me make a few observations.
I assume we are discussing open poses in the broadest possible sense, so as to include any pose which exposes the vulva and/or anus. I bring this up because a woman who is bending forward or down will expose her vulva and anus, as will a woman in a fetal position even though her legs are together.
These issues come up almost exclusively with regard to photography with female models. While male nudity is widely regarded as more shocking and more potentially obscene, certain objections are raised almost exclusively as regards female models. I have always found this amusing, since female genitalia are almost 100% internal and require gynecological or surgical instruments to see, so it is really the exterior and exposed part of the female body, and not the genitalia, which are at issue.
The real world is way ahead of this discussion. In the pages of Hustler, for example, vulvas and anuses are not just shown, but lately are shown being penetrated by fingers and tongues and penises and sex toys. The Internet newsgroups contain kiddie porn and necrophilia which go way beyond any question of mere nudity.
Someone once said that the Puritans condemned bull baiting not for the terror and agony it brought to the bull, but for the pleasure it brought to the spectators. In this context, it's clear that most of those who condemn open poses are puritanical.

DO OPEN POSES OPPRESS WOMEN?
Speaking for myself, when doing art erotica, the models are typically volunteers who do it because they enjoy it or because they want to see and possess the finished product. When doing commercial erotica on assignment, the models are normally paid by my client. In most cases, the payment is not great. Certainly, it's not great enough to induce the average female to shed her clothes and expose her genital area.
Quite frankly, most of my models would do open poses even without the financial incentive, because they enjoy being nude and specifically enjoy showing their naughty parts. I've even had models spontaneously masturbate in front of me, and for the majority who don't go quite that far, it's quite normal for them to lubricate. sometimes furiously. while posing. One volunteer model went through several dozen paper tissues during a 90-minute session.
Any woman or experienced male knows that lubrication is a sign of sexual excitement, not a sign of fear. The conclusion: the models (mine, anyway) enjoy being in front of the camera and showing it all.
Some feminists argue that all women are oppressed by erotic imagery of conventionally "pretty" women, and that explicitly and blatantly sexual images like open poses subject women as a group to standards of behavior most women can't (or don't want to) meet. If this is true, then by parity of logic I would be oppressed by the physical attributes and antics of Arnold Schwarzenegger and Johnny "Wadd" Holmes, and should probably be in a support group commiserating with other underdeveloped men.
I've been told that the real reason why "(m)ost women find these poses utterly repugnant" is that "the women in the photos don't seem to be in control." I don't think those who proffer this argument have seen the typical men's magazines, since most of the models bear expressions which seem to say, "If you want me, be prepared to beg." Even the relatively new "barely legal" category of magazines displays lovely 18 and 19 year olds who have virtually perfect little bodies and appear to be absolutely delighted to be in front of a camera.
Because I advertise for models, and don't approach young women on the street, every female who steps in front of my camera is there because she wants to be. And as I've said, I really don't pay all that well, so if a girl wanted to, she would have a very good reason for not posing for me. In my ad, or in the ensuing phone interview (which she initiates) I explain that there's no big pot of gold waiting for her and that arty stuff is often paid for in photos instead of cash. Perhaps there's a little disappointment, but it doesn't keep them from posing.
That so many have tells me that a certain segment of the female population simply can't wait to take its clothes off.
On those very rare occasions when I do see a magazine model who appears uncomfortable displaying herself, I feel bad for her. She shouldn't have been modeling and the photographer should have encouraged her to find some other way to make her money (because that's almost certainly the only reason she's doing it). Likewise, the creative director shouldn't have bought the photos. At the same time, though, by not pretending to know what is best for these young women, I show them a lot more respect than many of the so-called feminists and "advocates" who quite clearly would like to control my models into more demure behavior.

WHEN ARE OPEN POSES PORNOGRAPHIC AND/OR EROTIC?
In one of my shows I displayed a photo of an extremely beautiful woman laying on her back and splaying her inner labia. It was a fairly grainy 8x12 enlargement of a 35 mm Tri-X frame. While the pose was a standard men's magazine pose, it was in every other respect an art shot, which was the irony I was going for.
A lot of guys use photos of open poses as masturbation material. And making photos for this purpose is not such a terrible thing, since a man who has masturbated probably feels more like going to sleep than hurting anyone. The guys I worry about are the ones who can't masturbate and whose only sexual outlet must involve a female partner, even if she isn't consenting. Thus, my more "pornographic" work may actually be more socially redeeming than the gallery stuff!
As an aside, I have heard that the men's magazine poses are "too formulaic and unoriginal." It's too easy to say that these photos are unoriginal. Actually, these poses are conventions, not cliches, because they are all basically sex positions (if not for "normal" coitus, then for other forms of sexual contact). To anyone who's read the Kama Sutra, it quickly becomes clear why most of us use relatively few sex positions. As one gets away from the standard ones, they quickly become contortionistic and/or comical. While contortion has some kinky fetishistic appeal, comedy has none at all.
The point isn't to find a new position, we are stuck with only so many practical sex positions, but to take a familiar position and photograph it as well as we can. Conventions give art context and standards. And, sure, there are a lot of bad crotch shots out there, but I think probably 99.9% of all art is bad anyway.
In closing, let me return to the most overlooked reason for doing open poses: the models enjoy doing them! If the model is having fun and we are not harming anyone, mind your own damned business and find something really important to gripe about.

For Tom's work visit afterglow-photo.com

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