Patterns for successful wiki use
The gate anti-pattern involves putting up too many barriers to participation on the wiki. Gates are present when people have to go through a difficult account creation process that's not straightforward, have to undergo mandatory training, or have to have their contributions approved before posting them on the wiki.
If users have to fill out forms, or request permission, or get approval before being allowed to edit the wiki, then you've definitely set up too many gates.
Give every employee a wiki account by default. Make sure they have the most liberal permissions that you possibly can, and encourage the users to create a new wiki page or make an edit their very first day on the job. This will help them become comfortable with the using the wiki in their every-day work.