How can I set a default node owner for anonymous nodes on the node edit form?
You can do this pretty quickly in a custom module by implementing a hook_form_alter().

In this example, I created a module called "anon" (you might want to use something more specific) and in my anon.module, I have the following:

&lt;?php

/**
 * Implements hook_form_alter()     
 */
function anon_form_alter(&amp;$form, &amp;$form_state, $form_id) {
  global $user;
  if ($form_id == "article_node_form" &amp;&amp; isset($form['author']['name']['#default_value']) &amp;&amp; $form['author']['name']['#default_value'] == "") {
    $form['author']['name']['#default_value'] = $user-&gt;name;
  }
}


The above code checks to see if you are on a article_node_form (change this to the content type you are using), if the author of the form is blank (which is representative of an anonymous user) and then sets the author name to the currently logged in user name.

Note that by default a new form will always set the author value to the logged in user, so this would only apply for existing nodes.