Back in September 2016 the District Court in NSW made a ruling against a staff member who defamed his employer on his personal Facebook account.
The case was Rothe v Scott (No 4)  NSWDC 160. This is a precedent case in defamation laws as in that the employer was not specifically named in the Facebook post which is usually required to prove defamation.
The court ruled that there were sufficient facts in the post that an ordinary reasonable person could identify the subject of the post.
It is very important that you are always aware of you and your staff’s actions in and out of the workplace and that social media policies are incorporated into your employment contracts and office procedures.