Do I have a case for defamation?

Defamation, in its most basic form, generally requires the following elements: 1. The Defendant published a false statement; 2. About the Plaintiff; 3. To a third party; and 4. The falsity of the statement caused injury to the plaintiff. Most common issues with completing the necessary elements for defamation are either that the statement made by the potential Defendant was an option and not a statement of facts or that there was no injury to the potential Plaintiff.  In the situation you described, what I commonly see is that the statement made on Facebook, while perhaps untrue and downright mean, is an opinion.  Without seeing the posts or knowing more about you, I obviously can’t give an opinion on whether the statement is an opinion.  Another consideration is that even if you have a case, litigation is expensive.  Now, from a practical consideration, your first step should probably be to contact Facebook and make a complaint.  I believe they have a link from the homepage.  You mention that these statements are being made on other venues as well.  You may find spending some money to hire a lawyer for a cease and desist letter.  Oftentimes, these are enough to stop the conduct.