I'm thinking more in terms of syncing and storage. It all depends on how it's implemented. Does each community have a wiki that's synced with individual users' wikis? A separate wiki per instance? How to handle edit conflicts, etc.
You're right that just making a wiki isn't too tough, but in the case of decentralized, editable, moderated content, it's probably different enough to warrant an approach significantly different from a traditional, single site/many edit centralized version.
(We could always temporarily have a centralized wiki and roadmap out the transition later, too.)