Starting today, a Mozilla LDAP account with Mercurial SSH access is no longer required to hg push into MozReview to initiate code review with Mozilla projects.
The instructions for configuring your client to use MozReview have been updated to reflect how you can now push to MozReview over HTTP using a Bugzilla API Key for authentication.
This change effectively enables first-time contributors to use MozReview for code review. Before, you had to obtain an LDAP account and configure your SSH client, both of which could be time consuming processes and therefore discourage people from contributing. (Or you could just use Bugzilla/Splinter and not get the benefits of MozReview, which many did.)
I encourage others to update contribution docs to start nudging people towards MozReview over Bugzilla/patch-based workflows (such as bzexport).
Bug 1195856 tracked this feature.