The fake porn is just the tip of the iceberg. 
I can imagine some envious guy/gal that is annoyed the husband/wife of their coworker is married to such an annoying, incompetent person. They decide they need to give them a chance at a better partner, maybe them, and so they make some incriminating evidence and send it into the grapevine. People talk, and word gets around. Close friends feel the need to at least bring it up in case it's true. What will the wife/husband do? Are they partnered with a cheater? Can they be trusted? What if the entire relationship is a lie?
What if it wasn't actually AI and their partner has successfully convinced them it is?

 Relationship scams, destroyed relationships, reputation destruction, fake hostages, market upheaval, a withering of trust in institutions and other people, and, maybe someday, questioning the very notion of humanity as unique in any way (singularity territory), and many more things I am not yet cruel enough to imagine. Oh, the problems we face are only just getting started.