Well,we can't call famous authors to ask permission,but current writers on lj are accessible.Also, a published writer is used to having their work critiqued. A new or insecure writer is most likely not to view it the same way. It's different, I think with authors who are no longer around or who have left the fandom then it is for those who are still around. Those who are no longer writing for the fandom or who aren't on lj anymore probably wouldn't know or care one way or the other.
I would like to think that everyone would be mature about it,but I've seen some unfortunate things on lj that make me wonder sometimes. I'm all for stopping anyone who starts flaming right away.