Hook not getting called (image_title module)
Figured it out.  There was this crazy code in image_title_nodeapi():

function image_title_nodeapi(&amp;$node, $op, $teaser, $page) {
  if ( !user_access('create image titles') ||
       (variable_get('image_title_'. $node-&gt;type, 1) == 0) ) {    
     return; // do nothing ... 
   }


Which meant people could only see the images if they could also create images.  Not real bloody useful!  Fixed here:  https://github.com/kenahoo/drupal-image_title/commit/a4458676e7a6d1e00839a3d0e02a9d6c4f01fe2c

Update: on Paul's advice I created a fork in the Drupal Sandbox area: http://drupal.org/sandbox/kenahoo/1411716 .  I'm probably going to delete the github.com project now.