Who Should Be Responsible for a Brand's Social Media Outreach?

In the whole scheme of things, it should be the PR department...except that you are not going to find a PR department that knows how to do this job effectively. So, for the years 2008-2012, a firm would be better off starting a new department (or outsourcing the job to a group) made of managers and workers that have a familiarity with new technologies and user tendencies. But my guess is that after 2012 and beyond, this new department could be merged back into PR where it belongs as social media management becomes second-nature to the mission of Public Relations.