code: function updateUsername() {
        var $username = $el.findByName('username');
        if ((!usernameFocused) && (snippet.username === undefined)) {
          var username = apos.slugify($firstName.val() + $lastName.val());
          $.post(self._action + '/username-unique', { username: username }, function(data) {
            $username.val(data.username);
          });
        }
        $username.on('focus', function() {
          usernameFocused = true;
        });
      }
docs: Keep updating the username suggestion until they focus that field. Of course we don't mess with existing usernames.