Index: wp-includes/functions.php
===================================================================
--- wp-includes/functions.php	(revision 5775)
+++ wp-includes/functions.php	(working copy)
@@ -662,7 +662,11 @@
 }
 
 function wp_remote_fopen( $uri ) {
-	$timeout = 10;
+	$bytes_limit = 30720;  /* limit on size of source documen bytes, see 
+	                  	* Errata for pingback specification.
+				* http://www.hixie.ch/specs/pingback/pingback
+				*/
+	$timeout = 10; 
 	$parsed_url = @parse_url($uri);
 
 	if ( !$parsed_url || !is_array($parsed_url) )
@@ -678,7 +682,9 @@
 
 		//stream_set_timeout($fp, $timeout); // Requires php 4.3
 		$linea = '';
-		while( $remote_read = fread($fp, 4096) )
+		$bytes = 0;
+		while( $remote_read = fread($fp, 4096) && $bytes < $bytes_limit )
+			$bytes = $bytes + 4096;
 			$linea .= $remote_read;
 		fclose($fp);
 		return $linea;