I don't hide it, but then I also don't advertise it mostly because it is hard to explain to certain people and in that way it is not worth the effort of the explanation. It is something I do for fun and I am not ashamed of it and if it comes up in conversation I certainly mention it.  I do frame it as "Writing stories cooperatively with people on a forum" since that makes it more understandable to most people and keeps the misconceptions about RPing out of the discussion. So far it's worked for me.