Index: modules/data.eval.inc
===================================================================
--- modules/data.eval.inc	(revision 2890)
+++ modules/data.eval.inc	(working copy)
@@ -277,6 +277,20 @@
 }
 
 /**
+* Condition: List has count.
+*/
+function rules_condition_list_has_count($list, $value, $op = '==') {
+  switch ($op) {
+    case '==':
+      return count($list) == $value;
+    case '<';
+      return count($list) < $value;
+    case '>';
+      return count($list) > $value;
+  }
+}
+
+/**
  * Condition: Data value is empty.
  */
 function rules_condition_data_is_empty($data) {
Index: modules/data.rules.inc
===================================================================
--- modules/data.rules.inc	(revision 2890)
+++ modules/data.rules.inc	(working copy)
@@ -475,6 +475,32 @@
         'form_alter' => 'rules_data_list_form_alter',
       ),
     ),
+    'list_has_count' => array(
+      'label' => t('List has count'),
+      'parameter' => array(
+        'list' => array(
+          'type' => 'list',
+          'label' => t('List to check'),
+          'description' => t('A multi value data element to have its count compared, specified by using a data selector, e.g. "node:author:name".'),
+        ),
+        'value' => array(
+          'type' => 'integer',
+          'label' => t('Count'),
+          'description' => t('The count to compare the data count with.'),
+        ),
+        'op' => array(
+          'type' => 'text',
+          'label' => t('Operator'),
+          'description' => t('The comparison operator.'),
+          'optional' => TRUE,
+          'default value' => '==',
+          'options list' => 'rules_condition_list_has_count_operator_options',
+          'restriction' => 'input',
+        ),
+      ),
+      'group' => t('Data'),
+      'base' => 'rules_condition_list_has_count',
+    ),
     'text_matches'  => array(
       'label' => t('Text comparison'),
       'parameter' => array(
@@ -612,5 +638,16 @@
 }
 
 /**
+ * Options list callback for condition list_has_count.
+ */
+function rules_condition_list_has_count_operator_options() {
+  return array(
+    '==' => t('equals'),
+    '<' => t('is lower than'),
+    '>' => t('is greater than'),
+  );
+}
+
+/**
  * @}
  */