People shy away from what the law says because it's WIDE FUCKING OPEN with no guidelines for anything coherent. There's a ton and a half of case rulings, which contradict each other horrifically. (Copying an entire movie is okay with your VCR! But four notes of dubbing is illegal for a DJ! "Big Hairy Woman" is a parody, but "Cat NOT In The Hat" is infringement!)

And online, the law doesn't matter nearly as much as ISP/web host policy, because they're never required to allow all legal content. Part of what I *love* about Dreamwidth is that they started this fully aware of potential copyright claims against fandom, and were informed & ready to stick to "nope, they're not breaking any laws; we don't actually care how much their activities bother you."