When a group of friends decides to collectively cut off or limit contact and social interaction to a person.

When you eat dirt for the first time and leave your family to build a shack in the woods

When someone holes themself up in their room doing absolutely nothing at all when their friends all go out and do something fun. This is worse than being a video game nerd, because at least they are playing with other people. A social embargo has no even slight hint of social activity involved, and can therefore be employed easily without internet or communicatins of any sort.