Okay, now that everyone is blowing up about Lydia (and believe me, I am too), I would just like to compile the best of the best ideas I have seen into one massive theory.
First: yes, there is a sex tape. We will never see it, probably due to Darcy or Lizzie or - hey - maybe even Jane, if she grows some balls. (I really hope she does.)
Second: no, Lydia did not consent. I mean, come on, guys. There is no motivation behind her to consent. Besides, she and only she is in the headline. The ad for the tape is clearly centered on her and her alone.
Third: yes, Darcy can fix this. No, he cannot get rid of it, and I kind of doubt that he will be the one to destroy the tape. (If not Jane…Gigi?) However, there is one course of action left to Darcy, thanks to his wads of money: lawyers. That’s right, Darcy can help Lydia sue Wickham’s butt off. True, the law may not be entirely favorable of Lydia’s case due to her being 21, but Darcy and his lawyers can find a way, I’m sure.
Fourth: Wickham’s plot. To get money? I’m sure that is a factor, to be sure, but I don’t think it is the only one. I think this is revenge against Lizzie, for telling the true story of Darvid and Batman, and Darcy, for being so awesome. After all, it’s altogether too easy to plant the video and blame Lizzie for posting the tape. That way, he can all too easily emotionally wrangle Lydia into eloping with him. And I’m sure we all can imagine the damage he could do to the Bennet family from the inside.