Index: wp-includes/media.php
===================================================================
--- wp-includes/media.php	(revision 12478)
+++ wp-includes/media.php	(working copy)
@@ -954,6 +954,9 @@
 
 		// After a post is saved, cache oEmbed items via AJAX
 		add_action( 'edit_form_advanced', array(&$this, 'maybe_run_ajax_cache') );
+
+		// Convert YouTu.be URLs to normal ones
+		add_filter( 'embed_pre_url', array(&$this, 'youtube_url_expander') );
 	}
 
 	/**
@@ -1067,6 +1070,8 @@
 		$rawattr = $attr;
 		$attr = wp_parse_args( $attr, wp_embed_defaults() );
 
+		$url = apply_filters( 'embed_pre_url', $url );
+
 		// Look for known internal handlers
 		ksort( $this->handlers );
 		foreach ( $this->handlers as $priority => $handlers ) {
@@ -1194,6 +1199,16 @@
 		$output = ( $this->linkifunknown ) ? '<a href="' . esc_attr($url) . '">' . esc_html($url) . '</a>' : $url;
 		return apply_filters( 'embed_maybe_make_link', $output, $url );
 	}
+
+	/**
+	 * Convert YouTu.be URLs into their full length counterparts
+	 *
+	 * @param string $url A URL, maybe with youtu.be in it
+	 * @return string A URL, with any YouTube URL expanded
+	 */
+	function youtube_url_expander( $url ) {
+		return str_replace( 'http://youtu.be/', 'http://www.youtube.com/watch?v=', $url );
+	}
 }
 $wp_embed = new WP_Embed();