Ehh, even DeviantArt's policies are a little grey. I've seen some of the more popular artists (especially orpheelin) push the boundaries and then complain incessantly when some of it gets removed, though in a lot of cases, it does stay for whatever reason. There's an especially bad epidemic of especially cheap and tasteless, blatant cock-and-pussy shots that look more like they belong on the Myspace of genitalia than it does on a site promoting art. Unfortunately, with the "art" part of their name, they have to be careful of what they choose to keep and what has to go -- the adult filter certainly helps, and they also have an entire photography section for fetish material, so they're obviously not totally against sexual content (and one of my own risque pieces still remains untouched in my gallery), and they can't exactly discriminate on grounds of technical execution, either, or else aspiring artists who aren't terribly skilled, but are learning would be totally out. That's the beauty of having something as broad and undefined as 'art', I guess.
That being said, I have yet to find an avenue that is really best for selling art online. Adult art or no, I wouldn't recommend dA as your primary source...A lot of your success there relies on your advertisement elsewhere or your internal popularity with the community. I've done okay for myself there, but I had to do a ton of advertisement at other forums I frequent in order to direct attention at my dA page and also had my own friends on dA advertise me in exchange for me linking back to them. Add that in with dA's hit-or-miss adult content policy and you may find that it's not worth the headache.
You can try Etsy and eBay, though I think those services typically rely more on you sending out a physical copy, so if that's something you're considering, you could definitely try selling originals and commissions alike over there. Etsy, I think, is probably going to be easier to promote than eBay. I've really only seen friends of mine who are closer to professional status have any real success with eBay.
Depending on your genre of art, you might get lucky with Furbid...As the name implies, it's for furry art, and I'm pretty sure it can be sexual in content. Some of my friends who have dabbled in furries say the Furcadia community is especially profitable. Otherwise, I've sold art through forums I frequent -- be it MMOs I play/have played, video games I enjoy, or even the RP/writing places I post on. It can be time-consuming, it's important to build rapport and not just show up and say HI BUY MY ART, but you can sometimes find that if you establish yourself in a forum and garner the right attention without getting discouraged, it's easier to find clientele in your niche. And obviously, the more flexible you are with what you can draw and what genres you get into, that also opens up your options quite a bit.