I've never understood why, or even how fanfic could be written about real people. If you're going to write about characters in a show or something, I could see that. I used to be active in the XFiles fanfic world... Certain stories were good, others, not so good. Most of it was written about Mulder nailing Scully, or whatever, since philes are a bunch of pervs.
But, yeah, real people fic? Never got it. Never will.