Diana Gabaldon blew up over fanfic, describing her fans who wrote it as dirty porny unimaginative people fantasizing about her husband and coming to her house and selling her children into white slavery.
Ironically, she herself seems to have based her most famous creation on an actor she was a fan of, whose character she adapted for her own works.
Also, she praised her own son's book to outside sources while pretending they weren't related and he was this totally fantastic totally new author she just stumbled across. But that's really a different matter.