The problem always being, the fans, being fans, have extreme emotional investment in the things they have spent so much time watching/reading/listening, etc. They feel that particular something is "theirs", in the most abstract definition of the word. They feel they know more about the thing that those who actually own it do (which may be a correct statement) but in the full emulsion of that thing, they lose connection with the more objectively mundane legal aspects of that ownership.
"Fan" is the short form of the word "fanatic", after all.