
It can be argued that the two disciplines have different roles and serve different purposes.
The public relations practice according to PRSA is about reputation - the result of what you do, what you say, and what others say about you. Public Relations aims to earn understanding and support and influence opinion and behaviour.
While Social Marketing seeks to " influence social behaviours not to benefit the marketer ,but to benefit the target audience and general society.
This distinctive difference shows that social marketing has its place , public relations clearly outlines itself as a practice that is still needed for building relations with various publics.
References: What is Social Marketing by Nedra Kline Weinrich
Introduction to Public Relations by Sam Black
www.prsa.org