Please enable the new feature to email passwords based on email on the WMF wikis.
If I understand bug 13015 and the code correctly, this requires running patch-user_email_index.sql and setting $wgPasswordResetRoutes['username'] to true.
I think this will help keep sporadic editors and readers. I know I've sometimes forgotten usernames (on non-WMF sites). Right now, we tell such users we can't help them (http://en.wikipedia.org/wiki/Wikipedia:Contact_us/login_problems).
Version: unspecified
Severity: enhancement