Estee Lauder has recently fired one of their key senior executives over the content of a personal Instagram post.
Does your organization's enterprise risk management assessment include a section on social media? In responding to these positive and negative risks you must have a number of controls covering the entity and it's members.
Organizations have to properly protect themselves against risks and mitigate them to a point that is within the risk appetite of the leadership not the individual members.
Have your risk management experts, internal audit, provided a comprehensive review of the "Social Media" controls and their maturity. If not maybe that needs to be on the tactical audit plan.