The Apostate has a post about the tragic lack of nude men (at least, full frontal) in mainstream cinematic sex scenes, and why that is. The basic answer is that male bodies aren't objectified. Men aren't adjudged to be valuable based solely on their looks. Indeed, it is seen as weird and deviant to objectify male bodies. The Apostate urges that women start to break down the fiction that male bodies aren't the proper targets for objectification.
But wait, you say, if objectification is bad, then why is justifiable to do it to men? The answer is not that turnabout is fair play. Rather, it gets into the nuts and bolts of what it means to objectify someone, and how being seen as an object interacts with our sense of personhood and human dignity.
I've written before that, in contrast to what is maintained or implied by certain feminist theorists, being seen as an object -- the site of another's wants and desires, or a source of instrumentality to another's ends -- is an extremely important element of our personhood. Of course, it's not all we want -- we want also to be recognized as beings with inherent worth and human dignity, and we also want some level of control over how we are seen as valuable even as objects. But it is untrue to say that acknowledgment of subjective value is sufficient for our happiness. In order to be fulfilled, we need to be seen and perceive ourselves as being seen as both objects and subjects, at the same time.
In modern society, men (particularly White men) have many avenues through which both our objective and subjective value can be expressed and verified. The panoply of legal and moral rights, designed with men in mind, affirm that we are "God's children" and are beings worthy of inherent moral concern. The social structures we create also tell us, again and again, that we are useful creatures whose objective worth is articulated through prestige, awards, reimbursement, and acclamation.
The joke that is often laid about sexual harassment is asking a man "how would you like it if a woman told you you were attractive and she wanted to bone you?" It's an inapt comparison, though. Because seeing male bodies as "objects" (that is, entities which are wanted for the express purpose of fomenting pleasure in another) neither exhausts our dimensions of objective worth, nor operates to the exclusion of the recognition of our subjective value, it does not threaten to colonize male bodies in such a way that we are only seen as sex objects. A man whom women treat and talk about as hot still has fundamental ownership of himself, and is not limited to only that metric of worth. Taking it from another angle, it's not that women don't want to be seen as sexually attractive by men. What they protest is that being the totality of the avenues they have for attaining valuation.
I draw from all this that, in ideal circumstances, it is best for all parties when they are seen as objectively and subjectively valuable -- including on the axis of sexuality. Circumstances are not ideal when either element of valuation squeezes out the other -- as it is for women who are seen only as valuable along the object-axis (the definition of objectification). Men, though, by and large do exist in the land of ideals -- both of our objective and subjective value is pretty well established. So go ahead, women (hell, go ahead men) -- lust after me. I like knowing that I'm wanted, and I'm happy that you gain pleasure from wanting me. There's no threat here.
UPDATE: One more thing that came to me: it seems that people like to be objectively valued, but only if they have some degree of control over it. I might take pleasure in being valued for my contributions to Big Company, in part because I voluntarily chose to work for Big and can, if I choose, leave. Often times artists who are beloved by their audience members burn out because they get tired of only being seen as a tool for the desire's of the masses (think Dave Chappelle) and can never "turn it off". This goes back to the need for balance between objective and subjective valuation, and brings into play another dimension that must taken into account when noting the objective value of men.