I don't really agree that consent has to be obvious in the film itself. Some BDSM play and such doesn't have visual consent during the act - it is pre-discussed. So, films portraying that sort of interaction would want to have a true feel to it.
What about rape fantasies? Making a porn that portrays a fake rape isn't actually rape. It's someone agreeing to act like he/she is being violated while actually engaging in a consensual sex act for the camera.
I have no desire to watch either of those kinds of porn, but I don't have a problem with them being made and put out there for people who enjoy watching that kind of stuff.
Oh, and the Pirates ones I mentioned earlier -
and Pirates II: Stagnetti's Revenge
are fairly well-made films - they actually released versions that were rated R by taking out the sex scenes. Not a movie I'd watch just because (I mean, porn actors aren't really known for their ability to act in non-sexual scenes), but good.