Index: wp-admin/includes/class-wp-posts-list-table.php
===================================================================
--- wp-admin/includes/class-wp-posts-list-table.php	(revision 20330)
+++ wp-admin/includes/class-wp-posts-list-table.php	(working copy)
@@ -96,7 +96,7 @@
 		else
 			$total_pages = $wp_query->max_num_pages;
 
-		$mode = empty( $_REQUEST['mode'] ) ? 'list' : $_REQUEST['mode'];
+		$mode = empty( $_REQUEST['mode'] ) ? apply_filters( 'default-posts-list-mode', 'list' ) : $_REQUEST['mode'];
 
 		$this->is_trash = isset( $_REQUEST['post_status'] ) && $_REQUEST['post_status'] == 'trash';