From my perspective casual sex is that which takes outside of the marriage bed....and Ayn Rand in her writings and in her own life never advocated that position
Didn't Rand have an affair with Nathaniel Branden? (Granted, I'm coming in on the middle of a discussion, so if this has been brought up already, please disregard).
"Affairs are not the most dignified things, especially when carried on with someone twenty-five years junior, as Nathaniel Branden was to Rand, and especially when involving what appeared to be rough sex, that being the way Rand apparently wanted it."
http://www.missliberty.com/pageL.htm Don't get me wrong, I love reading Ayn Rand, have read five of her books (starting the sixth sometime this summer), and agree with much, but not all, of her philosophy. Just proves she WAS a human being, after all.
P.S. Sorry if the above was too explicit for anyone.