Well, this matter has always been a complicated one. It is related to many aspects of life values, and such values become releted to many diferent cultures. In our case (occidental society, wich is a male dominated one), i think prostitution and some other sexual behavior, is the result of treating sex out of its beautiful and natural meaninng. "Sexual Revolution", a book by Wilhem Reich gives a very good reflexions on this matters. As long as we treat "sex" as a natural fact, and behave accordingly, prostitution will no longer be necessary.