Some OnlineCommunities are CommunityOverContent. That is: the primary purpose of the community is orientated around members of the community, and the various artefacts produced by the community are regarded as side effects - potentially useful, but of no great value.
However, for some communities, the content produced is not a mere side-effect, but is the CommonCause: the thing that brings the community together in the first place. Here, the community is merely a means to the end of some valuable finished product, rather than an end in itself.
Wikis can be used in both forms, but have a number of advantages for ContentOverCommunity sites. The lack of technical editing restrictions detaches content from its original author(s), which helps reinforce the primacy of the content over those who merely create the content. Further, wikis can avoid hard distinctions between the content, and discussion about the content.
ContentOverCommunity sites tend to use some form of OpenContent license to grant the RightToFork - the negative consequences of forking on communities (cf ForkingOfOnlineCommunities) are less important than the benefits to the content. Other consequences of the low value placed on community are:
Examples: WikiPedia, Linux, workplace communities, ....