I just created https://www.facebook.com/MediaWikiProject . Then I (re?)discovered this other page that has all the popularity but seems to be unmaintained. I actually confused it with this other one claiming to be official, to which I had posted but I wasn't getting a reply... An on top of this there is this other page looking automatically generated, a Mediawiki developers group and perhaps more.
Anyway, discussion to merge or coordinate all these source is welcome.