=== modified file 'sites/all/modules/nat/nat.admin.inc'
--- nat.admin.inc	2010-07-15 11:50:29 +0000
+++ nat.admin.inc	2010-11-26 21:11:11 +0000
@@ -49,6 +49,13 @@ function nat_settings_form() {
       '#default_value' => isset($nat_config['delete'][$type]) ? $nat_config['delete'][$type] : 0,
       '#parents' => array('delete', $type)
     );
+    $form['nat_'. $type]['reuse_terms_'. $type] = array(
+      '#type' => 'checkbox',
+      '#title' => t('Reuse existing terms.'),
+      '#default_value' => isset($nat_config['reuse_terms'][$type]) ? $nat_config['reuse_terms'][$type] : 0,
+      '#description' => t('By default, new terms will always be created in the selected vocabularies, upon creating a new node (and during Sync). Checking this option will instead create an association to an <em>existing</em> term with the same name, if possible. (If multiple terms with the same name exist in a vocabulary, an association is made to one of the terms. Matching is case insensitive.)'),
+      '#parents' => array('reuse_terms', $type)
+    );
     $form['nat_'. $type]['related_'. $type] = array(
       '#type' => 'checkbox',
       '#title' => t('Allow users to define synonyms and related terms when they create and edit nodes.'),
@@ -77,6 +84,7 @@ function nat_settings_form_submit($form,
 
   $form_values['body'] = array_filter($form_values['body']);
   $form_values['delete'] = array_filter($form_values['delete']);
+  $form_values['reuse_terms'] = array_filter($form_values['reuse_terms']);
   $form_values['node_links'] = array_filter($form_values['node_links']);
   $form_values['related'] = array_filter($form_values['related']);
 

=== modified file 'sites/all/modules/nat/nat.module'
--- nat.module	2010-11-26 14:36:26 +0000
+++ nat.module	2010-11-26 21:11:39 +0000
@@ -488,11 +488,14 @@ function _nat_get_vocabularies() {
  */
 function _nat_add_terms($node, $vids = array()) {
   $nat_config = _nat_variable_get();
+  $existing_terms = array();
+  if (isset($nat_config['reuse_terms'][$node->type])) {
+    $existing_terms = taxonomy_get_term_by_name($node->title);
+  }
 
   $edit = array(
     'name' => $node->title,
     'description' => isset($nat_config['body'][$node->type]) ? $node->body : '',
-    'weight' => 0
   );
 
   $tids = array();
@@ -505,6 +508,15 @@ function _nat_add_terms($node, $vids = a
     unset($edit['tid']);
 
     $edit['vid'] = $vid;
+    $edit['weight'] = 0;
+    foreach ($existing_terms as $eterm) {
+      if ($eterm->vid == $vid) {
+        // Update the existing term, just as in _nat_update_terms()
+        $edit['tid'] = $eterm->tid;
+        $edit['weight'] = $eterm->weight;
+      }
+    }
+
     // Save hierarchy for vocabularies also present in the node form.
     if (isset($hierarchy[$vid])) {
       $edit['parent'] = $hierarchy[$vid];
@@ -606,6 +618,7 @@ function _nat_variable_get($name = NULL)
       'types' => array(),
       'body' => array(),
       'delete' => array(),
+      'reuse_terms' => array(),
       'related' => array(),
       'node_links' => array()
     );