Index: wp-admin/admin-ajax.php
===================================================================
--- wp-admin/admin-ajax.php	(revision 15043)
+++ wp-admin/admin-ajax.php	(working copy)
@@ -626,7 +626,8 @@
 	}
 
 	// We need raw tag names here, so don't filter the output
-	$return = wp_generate_tag_cloud( $tags, array('filter' => 0) );
+	$args = apply_filters('get_tagcloud_args',array('filter' => 0));
+	$return = wp_generate_tag_cloud( $tags, $args );
 
 	if ( empty($return) )
 		die('0');