This page will eventually be part of WikiMission.
Wiki has been pretty good at self-policing, in my experience. Tangents tend either to not go very far or to take twists and turns that intersect with the core themes. Of course, offering the opinion that a topic is not appropriate for Wiki is a part of self-policing. -- KielHodges
Wiki has found a scope that is neither too narrow nor too broad. I attribute this to a community seeking excellence in a medium that permits it. The result is a place that is neither wide open, nor easily characterized in how it might be closed. -- WardCunningham
To avoid a TragedyOfTheCommons, it may be useful to discourage large numbers of offtopic pages, and not starting other offtopic pages when the current number is too high. Avoid thinking, "I can post this because other people are offtopic". (FixBrokenWindows) -- AnonymousDonor
Wiki works analogously to a human mind, and a human mind works because of its wide associations and creativity, not by staying "on topic". Topics that don't interest a lot of readers and are not related to existing pages do not occupy a lot of Wiki's mind, neither conscious nor subconscious - see ForgetfulnessAsFilter, ThingsOnWikisMind. --FalkBruegmann
So, put more succinctly, in the beginning everything is OffTopic, and to create something (e.g. on a WikiForum), you render something OnTopic, see where it links out into the OffTopicness and see if you get support from the WikiCommunity. -- StijnSanders
Contrast: WikiForbiddenTopics