For me, I don't think of casual sex as being the same as anonymous sex. I think of it as on a "higher" level than that, in terms of being sex with someone I like, have good conversations, a sense of humor, some kind of connection, even if it is just the physical attraction or something rather "minor." But anonymous sex? Anon = totally unknown. What the hell is that, anyway? Is it like when I was 19 and going to discos and then out to the parking lot to get high and have sex in someone's car, and then go back inside to dance some more? Oh, gosh, the late '70s are very far away, I couldn't do that anymore. Is that what swing clubs are like, I wonder? But casual -- I can do casual, which I see as maybe a friendly flirtation that becomes something more, and you might see the person and hook up occasionally, without really knowing much about your lives, but that there's a mutual admiration or understanding between you. Maybe it's a coworker, someone on the periphery of your life, or whatever. A Friend with Benefits or a Fuck Buddy (are they the same thing?) is also casual sex to me. Now, would a "one-night-stand" be anonymous or casual in my view? Well, it depends on how well you connect. Sometimes the heart just reaches out and touches another unexpectedly, and it's a beautiful, casual, healing one-nighter.
I'm all for casual sex if the people involved have their heads screwed on right. I enjoy it, but I know it's not for everyone. I've said here before that I see sex as a form of communication, so you have to be clear in your intent, I think. For example, drunk sex (I mean sloppy drunk) with a stranger could be goofy fun but most likely hollow and unsatisfying because when you're that impaired, you're not really in touch with what is being communicated between you.
I do make a distinction between casual sex and casual relationships. So, where casual sex is above anonymous sex in my world view, casual relationships are another step higher. So, when I talk about my relationship with Shorty being casual, it isn't the same as just having casual sex with someone, at least to me. It is definitely more than that. To me, the sex we have is not casual. He has very patiently, deliberately, and lovingly opened me up to possibilities and new (for me) ways of being pleasured. It isn't just physical; it is giving and kind. We have a great deal of caring between us, and affection, and we talk about deeper feelings, and I know that if I were in a jam, I could call him. I think I could call him more often than I do, but I try to give him space. We are both free to see other people, and the relationship is what I call a casual relationship simply because he has an erratic, hectic schedule, and very little time in his life to see me, and so he cannot commit to anything on a regular, "serious" basis. He feels bad about this, so I know it is more than casual sex for him, too.