Splitting this out from #657472: Add setting to allow users to login with email address or username.
There's not much sense in the name being a hidden form field instead of an internal value of the form.
Now committed - http://drupalcode.org/project/email_registration.git/commit/738c003
Should be easy to backport after #1576666: Use hook_form_FORMID_alter.
Automatically closed -- issue fixed for 2 weeks with no activity.
Drupal is a registered trademark of Dries Buytaert.