I read about a set of exercises that works to channel sexual energy into spiritual energy, so that one can experience greater intimacy with GOD.
I believe that subconsciously this is what we humans are seeking from a sexual experience, and it is this longing for true love that can never be fulfilled by any human. This is why the sexual experience has to be done over and over again and yet is never really satisfying (on a soul level), unless it produces a child.
There is also the animal/creature element to our being that calls out to this aspect of us in order to be satisfied (physically), like any other bioligical impulse. This is the most dangerous I think.