Index: wp-includes/shortcodes.php
===================================================================
--- wp-includes/shortcodes.php	(revision 23394)
+++ wp-includes/shortcodes.php	(working copy)
@@ -232,6 +232,9 @@
 	$attr = shortcode_parse_atts( $m[3] );
 
 	if ( isset( $m[5] ) ) {
+		// see docs for WP_Embed::run_shortcode()
+		if ( $tag == 'embed' && $shortcode_tags[$tag] == '__return_false' )
+			return $GLOBALS['wp_embed']->run_shortcode( $m[0] );
 		// enclosing tag - extra parameter
 		return $m[1] . call_user_func( $shortcode_tags[$tag], $attr, $m[5], $tag ) . $m[6];
 	} else {