Punkin to clarify I don't think of your FWB as casual sex---what I meant by casual sex was meeting some dude you barely know and having sex and that being the end of it. It's just dangerous, really, as far as std's, whether or not he's an ax murderer, etc. I've had a fair number of former students who became friends who have done this sort of thing. They tend to say "if guys can do it, so can I" and inevitably they feel ashamed later (or have an STD sticking around).
I think the FWB with a long-time actual FRIEND with whom you have a relationship on some level is a whole different ballgame and one I'd probably explore if I had a guy friend who was single and willing :-)
M45 Bomb 6/09; EA 6/10; Divorced 1/11 Proud single mom of 7 little feline girls and one little feline boy "Fall down 53 times. Get up 54." -- Zen saying