@thomasfuchs there doesn't seem to be a lot of scientific evidence for it's effectiveness, though there's a lot of evidence for the harm it does.
There's also some evidence that it damages those who practice it.
It seems to me that for it to be effective, the shunned would need to not have another social group to retreat to, where they'd be accepted and even healed of the damage. They'd also need to deeply value the connection being broken.