Index: wp-includes/capabilities.php
===================================================================
--- wp-includes/capabilities.php	(revision 20373)
+++ wp-includes/capabilities.php	(working copy)
@@ -599,6 +599,18 @@
 	}
 
 	/**
+	 * Determine whether the user exists in the database.
+	 *
+	 * @since 3.4.0
+	 * @access public
+	 *
+	 * @return bool True if user exists in the database, false if not.
+	 */
+	function exists() {
+		return ! empty( $this->ID );
+	}
+
+	/**
 	 * Retrieve the value of a property or meta key.
 	 *
 	 * Retrieves from the users and usermeta table.