According to Google, HTTPS versions of our pages should have the rel=canonical head tag that points to the http version. See http://support.google.com/webmasters/bin/answer.py?hl=en&answer=139394
I can't remember that we ever had it like this, but if Google suddenly started enforcing this, then it might explain the http-https google split and google rank penalty that Wikid77 has been discussing on WP:VP/T.
Version: wmf-deployment
Severity: normal
URL: http://support.google.com/webmasters/bin/answer.py?hl=en&answer=139394
See Also:
https://bugzilla.wikimedia.org/show_bug.cgi?id=25882
https://bugzilla.wikimedia.org/show_bug.cgi?id=28602
https://bugzilla.wikimedia.org/show_bug.cgi?id=51002