fans and collaborative authorship

In his article "Models of Authorship in New Media," Manovich brings up "interactivity as collaboration between the author and the user" as another model of authorship. He uses focus groups as an example of this. However, in the last few years, these types of interactions are increasing and becoming even more collaborative. One particular example is the rise in prominence of fan culture. Snakes on the Plane, for instance, is an interesting case of viral marketing, as you all know. The most infamous line from the film, was shot afterwards based on a popular fan created internet video. There was also a music content, where the winners would be featured on the soundtrack of SoaP. Here, fans are literally contributing to the content of a work, so does this make them collaborators of the authors, or even the author themselves? What is happening to the line between author and user? Fans are feeling more agency towards the materials they're fans of, using the characters as their own, mimicking the author's styles, creating new styles. However, do these new examples overcome the notion that "the author and the user are often two toal strangers, two aliens which do not share a common communication code?" Is there equality between the two? I wonder this about fans, particularly with SoaP and what do they get out of it. For the studio, it's probably obvious. They get an automatic fan base, they get great advertising inexpensively. because fans feel a sense of ownership of the film as well, they become someone personally invested in the success of the film. They can make a profit. What do fans get out of this? Financially, not much. Do people write fan fic and make fan videos only because of their love of the material or for the potential of a margin of fame themselves, in internet communities? Is this enough? What becomes the relationship between author and user in these cases? Fans are inspired by what the author creates, the author appropriates the ideas of fans in the content, and fans view it and create more fan work. What becomes the outcome of this? Do works become more of a dialogue, an ongoing interaction?