Index: wp-admin/includes/meta-boxes.php
===================================================================
--- wp-admin/includes/meta-boxes.php	(revision 18662)
+++ wp-admin/includes/meta-boxes.php	(working copy)
@@ -527,8 +527,9 @@
 ?>
 <label class="screen-reader-text" for="post_author_override"><?php _e('Author'); ?></label>
 <?php
+	$who = 'authors';
 	wp_dropdown_users( array(
-		'who' => 'authors',
+		'who' => apply_filters('post_author_meta_box_who', $who),
 		'name' => 'post_author_override',
 		'selected' => empty($post->ID) ? $user_ID : $post->post_author,
 		'include_selected' => true