Someone from the Wikia team finally came up for air on the Lucene mailing lists. It was Dennis Kubes, and aside from being really busy (as one might expect :), it sounds like they're trying to do the right things for the open-source community: publish their improvements back to the community, etc.
lucene-java: Dennis Kubes, "Re: Wikia search goes live today" (Nabble archive)
An interesting detail:
"Also the social networking functionality, named foowi, will become its own open source project (probably with an apache license)"
"foowi", I like it! :)
Whilst searching Nabble for this to share, I happened upon an earlier message by Dennis asking about Wiki search, "Is anybody here working with that project or planning on working with it?". I can only assume that Jimbo Wales pinged Dennis personally sometime after Mar 25, 2007. :)
nutch-user: Dennis Kubes, "Wikia Search Engine? Anyone working on it?"