Forgot to reenable the export plugin.

apps/contacts/appinfo/remote.php

@@ -55,7 +55,7 @@ $server->addPlugin(new Sabre_DAV_Auth_Plugin($authBackend, 'ownCloud'));
 $server->addPlugin(new Sabre_CardDAV_Plugin());
 $server->addPlugin(new Sabre_DAVACL_Plugin());
 $server->addPlugin(new Sabre_DAV_Browser_Plugin(false)); // Show something in the Browser, but no upload
-//$server->addPlugin(new OC_Connector_Sabre_CardDAV_VCFExportPlugin());
+$server->addPlugin(new OC_Connector_Sabre_CardDAV_VCFExportPlugin());
 
 // And off we go!
 $server->exec();

apps/contacts/lib/sabre/vcfexportplugin.php

@@ -13,7 +13,7 @@
  * @author Evert Pot (http://www.rooftopsolutions.nl/)
  * @license http://code.google.com/p/sabredav/wiki/License Modified BSD License
  */
-class Sabre_CardDAV_VCFExportPlugin extends Sabre_DAV_ServerPlugin {
+class OC_Connector_Sabre_CardDAV_VCFExportPlugin extends Sabre_DAV_ServerPlugin {
 
     /**
      * Reference to Server class