It depends on how stringently you define "know." Any single interaction only exposes part of a person, and that's true face-to-face as well as online or in fanzines or correspondence.

By the standard you seem to be using, I don't know that many people, including many I've sat down over meals with. In fact, by that standard I'm not sure I know you.

As it happens, I don't think of myself as knowing rain_luong; I read Ozy and Millie and his LJ. But I knew papersky better before I'd been in the same room with her than I know the downstairs neighbor who drank tea and cried on my shoulder about her cat, and whose Hanukkah party I later attended.