Purposes

Shunning can be broken down into behaviours and practices that seek to accomplish either or both of two primary goals.

1. To modify the behaviour of a member. This approach seeks to influence, encourage, or coerce normative behaviours from members, and may seek to dissuade, provide disincentives for, or to compel avoidance of certain behaviours. Shunning may include disassociating the member by other members of the community who are in good standing. It may include more antagonistic psychological behaviours (described below). This approach may be seen as either corrective or punitive (or both) by the group membership or leadership, and may also be intended as a deterrent.
2. To remove or limit the influence of a member (or former member) over other members in a community. This approach may seek to isolate, to discredit, or otherwise dis-empower such a member, often in the context of actions or positions advocated by that member. For groups with defined membership criteria, especially based on key behaviours or ideological precepts, this approach may be seen as limiting damage to the community or its leadership. This is often paired with some form of excommunication.

[link to en.wikipedia.org]