When do I really need remove_filter or remove_action?

Hi!

I read a few tutorials that suggest you have to clean up your wordpress plugin (when deactivating) by removing all filters and actions that you have set. Is that right? I found nothing like that in other plugin-code… So when do I really need these functions?

This is my code until now:

<?php

/*
   Plugin Name: WordPress-Plugin Vorlage
   Plugin URI: http://www.iscope.de
   Description: WordPress-Plugin Vorlage
   Author: Fabian Heinrich <fheinrich@iscope.de>
   Author URI: http://www.iscope.de
   Version: 0.0.1
*/

if(!class_exists('myPlugin')) {

   class myPlugin {

      function __construct() {
         register_activation_hook( __FILE__, array(&$this, 'activate'));
         register_deactivation_hook( __FILE__, array(&$this, 'deactivate'));
      }

      function activate() {
         // hier setzen wir unsere Hooks, z.B.:
         add_action('edit_category_form', array(&$this, 'myHookCategory'));
      }

      function deactivate() {
         // hier räumen wir wieder auf, wenn das Plugin deaktiviert wird, z.B.:
         remove_action('edit_category_form', array(&$this, 'myHookCategory'));
      }

      function myHookCategory() {
         // hier kommt der Quelltext, den wir ins System bringen wollen
         echo '<h3>Mein erster Hook, yay!</h3>';
      }

   }

} else {

   $myPluginObject = new myPlugin();

   if (isset($myPluginObject)) {
      add_action('init', array(&$myPluginObject, 'activate'));
   }

}

?>

P.S.: Does someone know, why there is an add_action added after initializing the object? With initializing it, the constructor is called, isn’t it? So I dont understand that part…