The community has grown too large (see CommunityMayNotScale) or it has lost focus (see TargetReached). Perhaps the content is in some kind of CopyrightTrap that is hindering growth, or there are technology-based problems with the old location. Perhaps the community is suffering under a GodKing or an AbsentLeader.
Therefore, StartAgain. Dissolve the community and start another one. Remember that TheCollective is mobile, and can change the pub. Try to retain the best elements from the old community, while removing problems. Retain links to the old content by InterWiki techniques such as UnifiedRecentChanges and NearLinks.
If the problem is due to the size of the community, then carefully select the new members and let the word spread through personal communication. In a sence, this is a GatedCommunity, where the barrier to entry is its obscurity. The big problem with starting from scratch is the loss of all those readers and editors from SearchEngine coverage, bookmarks, links etc. However, if the problem is an excess of readers, these problems become benefits!
But, be warned that ForkingOfOnlineCommunities can be bad. This should be considered a last resort, when other approaches have failed. Aside from the loss of readers (which may not be what you want), you also face the legal problem of getting out of the CopyrightTrap.
The above text is PrimarilyPublicDomain
Define external redirect: CategoryCommunityStrategy