diff --git wp-includes/pluggable.php wp-includes/pluggable.php
index ac308a9..11d769f 100644
--- wp-includes/pluggable.php
+++ wp-includes/pluggable.php
@@ -133,15 +133,21 @@ if ( !function_exists('get_user_by') ) :
  * @return bool|object False on failure, WP_User object on success
  */
 function get_user_by( $field, $value ) {
+	static $cache = array();
 	$userdata = WP_User::get_data_by( $field, $value );
 
 	if ( !$userdata )
 		return false;
 
+	$key = $field . '|' . $value;
+	if ( isset( $cache[$key] ) )
+		return $cache[$key];
+
 	$user = new WP_User;
 	$user->init( $userdata );
 
-	return $user;
+	$cache[$key] = $user;
+	return $cache[$key];
 }
 endif;