Social Networking & Professional Responsibility

I have been driving the use of Microblogging with a few departments (obviously Talent Acquisitions is one) in my company. We have been utilizing social networking sites and blogging for a while. It has brought to mind that we as a company should update our policy on social media. My fear was not with the recruiters. They have been out there representing our brand well for years. What about other employees? Do they understand their responsibility when they attach our company to there profile and answer a question on as a representative of the corporation? My question is DO they have a responsibility and where does that responsibility end?

I am not talking about censorship; I am talking about being professionally responsible while representing your company’s brand. What are the lines between personal “tweet’s” and unintentionally hurting the company you loves brand.