Assessing the credentials of internet pornography

I don't know a whole lot about pornography as I'm not exactly in the market for it. But I do know several things:

1. There is a wide variety of pornography available on the internet.
2. Some of this pornography is "legitimate", i.e. the participants knew and consented to the fact that they were appearing in pornography for general distribution.
3. Some of this pornography is "illegitimate", i.e. the participants did not know about, did not consent to, or did not understand the implications of either the sexual acts themselves, or the fact that the sexual acts were being recorded, or the fact that the recordings were being widely distributed.
4. Pornography is distributed through a wide variety of media of varying degrees of legitimacy, ranging from official websites belonging to official producers of pornography, to usenet, to file-sharing software, to various web communities.
5. As with the sharing of other types of files, perfectly legitimate pornography can be exchanged through illegitimate means, and illegitimate pornography can also be exchanged through the same legitimate means.
6. For some users, it is important that all the pornography participants be willing and consenting. I myself know some individuals for whom pornography is a turn-on, but the thought of people being forced into sex acts or taped without their consents is a turn-off.

This all raises the question: how does a user know that pornography acquired through the internet is, in fact, perfectly legitimate and all the participants are consenting? If the pornography is acquired through not-entirely-legitimate means you can never be sure where it came from, and it wouldn't be that hard to make something taped candidly look professional in post-production, even imitating features of well-known professiona pornography producers. I guess I'm surprised that people who are capable of enjoying pornography but incapable of enjoying non-consentual or otherwise "illegitimate" pornography are still able to use and enjoy material gather from "illegitimate" internet sources.