Employees telling the truth in social media (isn't that kinda the point?)

What's the role of a social media representative - to repeat the press releases on Twitter? Or to engage with customers who have unpleasant feedback to share? Something in the middle?

I don't think one answer suits all companies - every culture is different - but I have to imagine that any company employing an "online customer presence," using social media, should be ready to accommodate and engage negative feedback - even from the social media rep.