I saw on one of my LinkedIn groups a discussion about whether social media be the preserve of PR or Marketing. The discussion ranged from comments making points like PR should be central as they are the professional communicators, through to issues of corporate culture and structure.
Many organisations have divided up the responsibilities on-the-hoof, giving only lip service to any sort of structure. The one thing which I feel really needs to be highlighted is the necessity for a social media plan. Within the larger organisation aspects of social media need to be addressed by different parts; is it a customer service issue, a corporate issue or something involving a community outreach? Organisations need to have proactive and reactive elements; crucially involving a gatekeeper/filter to see that all proactive elements are complimentary and reactive points are all addressed.
While this is new to many organisations, alot are doing it really well, learning quickly, having a plan and adapting it to the changing style of external contact where the organisations reputation is increasingly coming under the ownership of its publics.