Enterprise wikis are often private. We will comb through the list of Fortune 1000 companies and try to identify companies that use MediaWiki.
Our initial research of a Fortune 1000 list confirmed that enterprise wikis are indeed difficult to find through basic or conventional search methods.
Creativity is needed to find these wikis. This task has been submitted for Google Code-in 2014 as a project that volunteers could help with. See T1340: Mentor Student(s) Who Will Help Identify Enterprise Wikis from List of Fortune 1000