I read about these potlatches in a sociology class Faldage. They were also used to lord one tribe's superiority over another.

When a tribe wanted to quash a neighboring tribe, they'd invite them over and lavish an inordinate amount of gifts on them. If the neighboring tribe could not top the gift-giving feast in a specific amount of time (I don't remember exactly how long it was) then the tribe would lose face and be considered inferior.