Here's an incremental diff of the changes that Gavin suggested on IRC:

=== modified file 'lib/canonical/launchpad/javascript/bugs/bugtask-index.js'
--- lib/canonical/launchpad/javascript/bugs/bugtask-index.js	2009-11-17 16:00:21 +0000
+++ lib/canonical/launchpad/javascript/bugs/bugtask-index.js	2009-11-18 15:20:12 +0000
@@ -54,8 +54,7 @@
 Y.augment(PortletTarget, Y.Event.Target);
 Y.bugs.portlet = new PortletTarget();
 Y.bugs.portlet.subscribe('bugs:portletloaded', function() {
-    setup_subscription_link_handlers();
-    load_subscribers_from_duplicates();
+    load_subscriber_ids();
 });
 Y.bugs.portlet.subscribe('bugs:dupeportletloaded', function() {
     setup_unsubscribe_icon_handlers();
@@ -78,6 +77,22 @@
     setup_unsubscribe_icon_handlers();
 });
 
+/* If loading the subscriber IDs JSON has succeeded, set up the
+ * subscription link handlers and load the subscribers from dupes.
+ */
+Y.bugs.portlet.subscribe('bugs:portletsubscriberidsloaded', function() {
+    setup_subscription_link_handlers();
+    load_subscribers_from_duplicates();
+});
+
+/* If loading the subscriber IDs JSON fails we still need to load the
+ * subscribers from duplicates but we don't set up the subscription link
+ * handlers.
+ */
+Y.bugs.portlet.subscribe('bugs:portletsubscriberidsfailed', function() {
+    load_subscribers_from_duplicates();
+});
+
 /*
  * Subscribing someone else requires loading a grayed out
  * username into the DOM until the subscribe action completes.
@@ -1806,35 +1821,44 @@
         Y.bugs.portlet.fire('bugs:portletloaded');
     }
 
-    function load_portlet() {
-        var config = {on: {success: setup_portlet,
-                           failure: hide_spinner}};
-        var url = Y.get(
-            '#subscribers-content-link').getAttribute('href').replace(
-                'bugs.', '');
-        Y.io(url, config);
-    }
+    var config = {on: {success: setup_portlet,
+                       failure: hide_spinner}};
+    var url = Y.get(
+        '#subscribers-content-link').getAttribute('href').replace(
+            'bugs.', '');
+    Y.io(url, config);
+};
 
-    function load_subscriber_ids(transactionid, response, args) {
+function load_subscriber_ids() {
+    function on_success(transactionid, response, args) {
         try {
-            var subscriber_ids_node = Y.Node.create(
-                response.responseText);
-            var subscriber_ids_json = subscriber_ids_node.get('innerHTML');
-            subscriber_ids = Y.JSON.parse(subscriber_ids_json);
+            subscriber_ids = Y.JSON.parse(response.responseText);
+            Y.log("Loaded subscriber IDs.");
+
+            // Fire a custom event to trigger the setting-up of the
+            // subscription handlers.
+            Y.bugs.portlet.fire('bugs:portletsubscriberidsloaded');
         } catch (e) {
             Y.log("Unable to load subscriber ids.", "error");
+
+            // Fire an event to signal failure. This ensures that the
+            // subscribers-from-dupes still get loaded into the portlet.
+            Y.bugs.portlet.fire('bugs:portletsubscriberidsfailed');
         }
-
-        load_portlet();
-    }
-
-    var config = {on: {success: load_subscriber_ids,
-                       failure: load_portlet}};
+    }
+
+    function on_failure() {
+        // Fire an event to signal failure. This ensures that the
+        // subscribers-from-dupes still get loaded into the portlet.
+        Y.bugs.portlet.fire('bugs:portletsubscriberidsfailed');
+    }
+
+    var config = {on: {success: on_success,
+                       failure: on_failure}};
     var url = Y.get(
         '#subscribers-ids-link').getAttribute('href').replace('bugs.', '');
-    Y.log("Getting ids from " + url);
     Y.io(url, config);
-};
+}
 
 }, '0.1', {requires: ['base', 'oop', 'node', 'event', 'io-base', 'json-parse',
                       'substitute', 'widget-position-ext',

=== modified file 'lib/lp/bugs/browser/bugsubscription.py'
--- lib/lp/bugs/browser/bugsubscription.py	2009-11-17 14:58:39 +0000
+++ lib/lp/bugs/browser/bugsubscription.py	2009-11-18 15:20:12 +0000
@@ -106,6 +106,10 @@
         """Return subscriber_ids in a form suitable for JavaScript use."""
         return dumps(self.subscriber_ids)
 
+    def render(self):
+        """Override the default render() to return only JSON."""
+        return self.subscriber_ids_js
+
 
 class SubscriptionAttrDecorator:
     """A BugSubscription with added attributes for HTML/JS."""

=== modified file 'lib/lp/bugs/browser/configure.zcml'
--- lib/lp/bugs/browser/configure.zcml	2009-11-17 14:58:39 +0000
+++ lib/lp/bugs/browser/configure.zcml	2009-11-18 15:20:12 +0000
@@ -1008,7 +1008,6 @@
             for="lp.bugs.interfaces.bug.IBug"
             name="+bug-portlet-subscribers-ids"
             class="lp.bugs.browser.bugsubscription.BugPortletSubcribersIds"
-            template="../templates/bug-portlet-subscribers-ids.pt"
             permission="zope.Public"/>
         <browser:navigation
             module="lp.bugs.browser.bug"

=== removed file 'lib/lp/bugs/templates/bug-portlet-subscribers-ids.pt'
--- lib/lp/bugs/templates/bug-portlet-subscribers-ids.pt	2009-11-17 14:58:39 +0000
+++ lib/lp/bugs/templates/bug-portlet-subscribers-ids.pt	1970-01-01 00:00:00 +0000
@@ -1,6 +0,0 @@
-<div
-  xmlns="http://www.w3.org/1999/xhtml"
-  xmlns:tal="http://xml.zope.org/namespaces/tal"
-  xmlns:metal="http://xml.zope.org/namespaces/metal"
-  xmlns:i18n="http://xml.zope.org/namespaces/i18n"
-  tal:content="view/subscriber_ids_js" />