Content lost in 2007
On September 3rd, 2007 the original UseModWiki software that ran MeFi Wiki was replaced with MediaWiki. While there were several reasons for the migration, one major reason was that the version that ran UseModWiki suffered from serious spam problems. Due to the way UseModWiki discarded older revisions of pages, edits by spammers actually destroyed some of the content on the original wiki.
Through the efforts of a number of volunteers, most of the former content was preserved, although some was lost forever. If you're looking for something in particular, you might be able to find it at archive.org. If you ended up here by trying to follow a link to the original wiki from the MetaFilter archives, it's possible that your desired content still lives somewhere in the wiki. Try searching the wiki.