Let's take a hypothetical case.
You have a man who is proud. Very proud.
He, for whatever reason, gets involved in sins of the flesh. Let's say his guilt extends even to the vice of sodomy.
Let's also say that the man keeps his shameful deeds between himself and his "partner" (or his victim!) -- he feels no need ever to videotape anything. Now this latter detail isn't that much of a stretch to imagine -- because, for certain deeds, human nature itself inclines toward privacy!
Fast forward a few months or years -- Let's say a few people accuse him of sodomy in an open forum.
Wouldn't this man be quite bold in his denials, knowing that there is NO WAY POSSIBLE for anyone to bring forth proof of his assertion? Even if the accused man in question wore lip gloss, nothing but pink clothing, and his favorite musical artist was Britney Spears -- any accusations of sodomy would be based on conjecture, not proof.
Just some food for thought.