I am the co-maintainer of an OpenSource project called AwesomeWM. I took down our wiki years ago due to:

* Constant vandalism

* Dubious user created content rendering computer non functional

* Trolling edits to cause breakages to people copy/pasting shell commands

* SPAM

* Maintaining the wiki

Before that we forced users to log-in for edits, then forced moderator approvals for everything, then forced moderator approval for new account. Then gave up and retired the Wiki.

So no, wiki are not free content. They are a pain, especially when your community tend to have many trolls/hostile individuals like the gaming community. It's not "downright lies" all the time.