Look, I think fan fiction is a great thing. People have been writing fan fiction for as long as there's been stories — you could make a very compelling case for playwrights and poets telling multiple versions of the same stories as an early draft of fan fiction.
But there is a bit of a "controversy" circling the most recent Star Wars film, The Last Jedi, and I think it's ludicrous. Fans are claiming that Rian Johnson, the writer/director of Jedi, plagiarized the film from a work of fan fiction published right after the release of the first film in the modern Star Wars trilogy, The Force Awakens.
Here's a long post outlining the similarities between the film and the fan fiction. (Spoiler warning, obviously, if you haven't seen Jedi and still plan to.) The similarities include a character fighting with a staff, formerly deceased characters returning as ghosts, and an arrogant character being busted down to a lower rank due to their hotheaded nature. The post ends, "I think Lucasfilm has some explaining to do."
Look: the dirty little secret about writing is that ideas are impossibly cheap. An idea is nothing, and what most writers call "inspiration" is simply an idea that thinks a little too highly of itself. The fact is that if an idea ocurred to you, it has likely occurred to someone else. In writing, it's what you do with the idea that matters most.
Am I saying that nobody, in the history of writing, has ever plagiarized an idea from another writer? Of course not. You can find exceptions to prove the rule anywhere you look. But for a proven writer/director — Looper is one of the best original sci-fi films of recent years — to willingly crib ideas from a fan fiction that is relatively popular in the fan community for use in one of the most anticipated films of the decade would be a spectacular brand of career suicide.
Let's pretend for a moment that Johnson was trawling fan fiction for ideas for Jedi, even though most writers on an IP would likely avoid fan fiction as though it were poisonous for this very reason. And let's say Johnson did find the stories in this fan fiction to be absolutely irresistable. The most likely course of action then would be to track down the writer and get them a story credit on the film. That would be a much cheaper course of action than whatever the settlement from a plagiarism suit would cost.
Fan fiction is fun, and it's a great way to practice writing and build an audience. But to add another layer to fan fiction with an elaborate plagiarism conspiracy theory seems unproductive. We don't need more people on the internet crawling up their own butts like this. We need people writing and putting creativity into the world.