Index: wp-admin/includes/user.php
===================================================================
--- wp-admin/includes/user.php	(revision 17347)
+++ wp-admin/includes/user.php	(working copy)
@@ -278,7 +278,10 @@
 	do_action('delete_user', $id);
 
 	if ( 'novalue' === $reassign || null === $reassign ) {
-		$post_ids = $wpdb->get_col( $wpdb->prepare("SELECT ID FROM $wpdb->posts WHERE post_author = %d", $id) );
+		$post_types_to_not_delete = apply_filters( 'delete_user_not_these_post_types', array( 'nav_menu_item' ), $id );
+		$post_types = array_diff( get_post_types(), $post_types_to_not_delete );
+		$post_types = implode( "', '", $post_types );
+		$post_ids = $wpdb->get_col( $wpdb->prepare("SELECT ID FROM $wpdb->posts WHERE post_author = %d AND post_type IN ('$post_types')", $id) );
 
 		if ( $post_ids ) {
 			foreach ( $post_ids as $post_id )