? optional_vocab.patch
Index: views/modules/views_taxonomy.inc
===================================================================
RCS file: /cvs/drupal-contrib/contributions/modules/views/modules/views_taxonomy.inc,v
retrieving revision 1.27.2.10
diff -u -p -r1.27.2.10 views_taxonomy.inc
--- views/modules/views_taxonomy.inc	5 May 2007 00:52:29 -0000	1.27.2.10
+++ views/modules/views_taxonomy.inc	22 May 2007 22:49:12 -0000
@@ -240,7 +240,9 @@ function views_taxonomy_form(&$vocabular
     $form = taxonomy_form($vocabulary->vid, 0, $vocabulary->help);
     unset($form['#title']);
     unset($form['#description']);
-    unset($form['#options'][0]);
+    if (!$vocabulary->required) {
+      unset($form['#options'][0]);
+    }
     $form['#multiple'] = TRUE;
   }
   return $form;