We had someone who became mentally unstable on staff and they mounted a full on campaign against the company online whilst still employed. This included impersonating executives, other employees and key customers on social media and other things meant to damage our image. They got a sum ~30% of their annual salary and we got a non disparagement agreement. They were let go as part of that. 1 month later they were at it again and we were able to get our money back. Right before it bankrupted them...guess what stoped happening. We dropped it without taking a cent of their money (we wouldn't actually do that) Hasn't been a problem.
They can be absused, sure but there are legitimate uses too.