Lowest number of news items selectable for display in block is 2. Why not 1?

Is there any reason why this is set to prevent a user from selecting a single RSS item?

>> '#options' => drupal_map_assoc(range(2,20)) (near line 364, http://api.drupal.org/api/drupal/modules%21aggregator%21aggregator.modul... )

What will break outside of this module if I change it to (1,20), if anything?