It seems that since sometime around February no new "autocreate" events are logged to the database on WMF wikis.
I'm not sure if this is a CentralAuth bug (it seems CentralAuthHooks.php hasn't been touched for a while), but I couldn't find anything in User.php either... maybe also a WMF-only bug, I didn't test the latest SVN version.
Version: unspecified
Severity: enhancement
URL: http://en.wikipedia.org/wiki/Special:Log/newusers