lynxgriffin:

A lot of it is more unspoken policy than outright stated, but yeah, especially if you’re a writer/director/lead on a show, you can’t read fanfic. It’s not just for hypotheticals either; there is legal precedence for when this sort of thing has happened in the past, although I don’t remember the details now. It’s just a lot better for people on a show to not give themselves a potential legal headache, even unintentionally. 

someone told their star trek fanfiction to will shatner which coincidentally had a similar plot to an episode that was already filmed and not yet released. the fan tried to sue the company claiming they stole the story from the fanfiction. the studio was able to prove that it was filmed before the fanfiction was shown to shatner but it was still a pretty close call.