Dangers of pornography are things like addiction, as people have already discussed; they're also things that don't effect the end user/consumer so much, like the abuse and neglect of actors and actresses, violence against these people, and the way this impacts the justice system and health system like any other act of abuse/violence. Of course, there's legal recourse for these people, who can go to that justice system and say 'look, I consented to be in an adult film, and then they beat the hell out of me against my will' or 'they beat me off screen because I wasn't doing exactly what they wanted', etc. This isn't reason to restrict pornography... this falls into a seperate legal realm altogether. People have the right to safe work. Your boss in your office wouldn't get away with beating the tar out of you if you didn't do something, so why should a pornographer be allowed to get away with the same?
Alleged danger number two, the constant suggestion that pornography leads to rape is, I think, misguided at best and completely flawed and erroneous at worst, and I'm glad noone brought that up because it just isn't a logical conclusion of this - no moreso, anyway, than someone saying 'yeah, well, every hour someone watches porn they aren't out raping someone' as if rape is the logical result of any given person's day. It's a possibility, don't get me wrong, but it is more likely that someone will develop a domination fetish, rather than go completely wacky. You have to be a pretty serious addict, and have pretty serious mental issues, to start ignoring the laws of reality. Porn should be self-evidently surreal; nothing that ever happens in porn happens in real life, the way it happens in real life. On one level, its almost a romantic ideal of sex and sexuality, and on the other hand, its a horrible (sometimes perverse) mockery of that ideal - that, plus a blind monkey could write a porn script.
Like Beli, I don't really consider explicit sexual content to be pornography... sure, its hokey and unrealistic, but isn't that the point? Sure, there's no 'love' element to porn, but you're either marketing this stuff to single people, or you're marketing it to people who are married and 'love' someone else (I say that guardedly, as some couples are okay with watching porn together, some are okay with it in general, and for others its a strict no-no). Sex really does have to have a violent content to get under my skin, and even that, the context of the 'violence' must be considered... Is the violence social/psychological, like the reduction of men and women to mere sex objects to be played with, dominated, and discarded? Sure there is, but that's no different from any other media institution which uses sex sells advertising; I mean, at least pornography doesn't try to cover it up, they do it explicitly almost to the point of hyperbole. No young woman, anywhere, ever, looks up with doe eyes at 3 fat fifty year old men and says 'ohhhh, fuck my ass' while someone grabs her throat. If reality is right here, pornography is off in la-la land somewhere around the moon. Pornography does not have real-world implications in the sense that it is realistic and should be emulated - no moreso than magic wizards casting fireballs in a fantasy novel. That's what this is, anyway, pornographers sell their audience a fantasy. The real-world implications come from the fact that people lack the ability to seperate fantasy from reality and -will- try to emulate it anyway, or will come to believe that this is 'how sex is'. I'm not sure that this is the responsibility of the pornography so much as the education system breeding people not to gain independant analytical thinking skills. Like, where is BDSM okay, and where is it 'violent'? Obviously you can't get to the point of snuff films and whatnot without drawing that line, but I'm not sure you can really draw the line before people start truly being 'hurt', as you can never really fully comprehend from the context of an edited film just what exactly was going on in the room at the time. Some people like BDSM, and some of them will watch BDSM films when not engaging in BDSM. This doesn't by necessity make BDSM 'wrong' or dangerous. The same people who think video game violence is real, or that you can dodge bullets like in movies, are the same people who pose a threat to the rest of us when exposed to 'violent' pornography.
So for me, censoring that sort of thing is completely arbitrary... sure, the line has to be drawn when people die (as in snuff films) but up to that point people can consent to participate in as much violence as they like... What about boxing? Hockey? Wrestling? Ultimate Fighting Challenges? Why not sex? I'm not even sure that violence is a proper qualifier, nor the way that it effects the audience. Not because the possibility is there that someone might get hurt against their will - this is a possibility of any situation, anywhere, at any time, and not a reason to start prohibiting things. It shouldn't be restricted simply on the basis that you'd be restricting something free of ill intent or harm. Without the harm component, you'd basically be saying you can censor anything you find distasteful and don't personally enjoy, even if you let some things go because you know others enjoy them; it'd still have that arbitrary bit in there that's hard to work out. I'm more on the side of continuing to make pornography available strictly to legal adults, continue to prosecute pornographers who break the law; with the addition that actors/actresses should be educated of their legal rights and responsibilities, and that the end consumer should be informed of the potential for pornography to disrupt family life and to form perception altering psychological addictions and so on.
I've always been a fan of 'try educating people about the harms something can cause, and how to use something responsibly' than outlawing it. Pornography isn't going to go away, so we have to learn to deal with it; and as nice as it would be if we could just close our eyes and will away our problems, that's really not going to happen. Restrictions do, I think, just exacerbate the problem rather than mitigating it in cases like this. You push people underground, you alienate them, and you make it unsafe for people to participate in making/procuring/consuming as people will worry about 'going to jail' or 'getting a fine' before they worry about their own well-being in the event that problems arise; this should never -ever- happen. An open forum for discussion on the issue is far more useful than making it taboo and trying to use social pressure to make people conform - this may have worked 200 years ago, but given the luxury available to the individual in the privacy of his/her home in this day and age, I don't think that there's really any way to regulate private actions and social pressure just isn't up to snuff for the job.
But anyway... sorry that's so long :\ I just didn't want to be too brief and make unclear points... if I can clarify anything, let me know.