function PO_backupBookmarks() {
    var fp = Cc["@mozilla.org/filepicker;1"].createInstance(Ci.nsIFilePicker);
    fp.init(window, PlacesUIUtils.getString("bookmarksBackupTitle"),
            Ci.nsIFilePicker.modeSave);
    fp.appendFilter(PlacesUIUtils.getString("bookmarksRestoreFilterName"),
                    PlacesUIUtils.getString("bookmarksRestoreFilterExtension"));

    var dirSvc = Cc["@mozilla.org/file/directory_service;1"].
                 getService(Ci.nsIProperties);
    var backupsDir = dirSvc.get("Desk", Ci.nsILocalFile);
    fp.displayDirectory = backupsDir;

    fp.defaultString = PlacesUtils.getBackupFilename();

    if (fp.show() != Ci.nsIFilePicker.returnCancel) {
      PlacesUtils.backupBookmarksToFile(fp.file);

      // copy new backup to /backups dir (bug 424389)
      var latestBackup = PlacesUtils.getMostRecentBackup();
      if (!latestBackup || latestBackup != fp.file) {
        latestBackup.remove(false);
        var name = PlacesUtils.getBackupFilename();
        fp.file.copyTo(this.bookmarksBackupDir, name);
      }
    }
  };
  PO_backupBookmarks()