diff --git a/mod/forum/lib.php b/mod/forum/lib.php
index b943b78e250..f20f1f0b20c 100644
--- a/mod/forum/lib.php
+++ b/mod/forum/lib.php
@@ -70,8 +70,14 @@ function forum_add_instance($forum) {
         }
     }
 
-    if ($forum->forcesubscribe == FORUM_INITIALSUBSCRIBE) { // all users should be subscribed initially
-        $users = get_course_users($forum->course);
+    if ($forum->forcesubscribe == FORUM_INITIALSUBSCRIBE) {
+    /// all users should be subscribed initially
+    /// Note: forum_get_potential_subscribers should take the forum context,
+    /// but that does not exist yet, becuase the forum is only half build at this
+    /// stage. However, because the forum is brand new, we know that there are
+    /// no role assignments or overrides in the forum context, so using the
+    /// course context gives the same list of users.
+        $users = forum_get_potential_subscribers(get_context_instance(CONTEXT_COURSE, $forum->course), 0, 'id, email', '');
         foreach ($users as $user) {
             forum_subscribe($user->id, $forum->id);
         }
@@ -282,7 +288,8 @@ function forum_cron() {
 
             // caching subscribed users of each forum
             if (!isset($subscribedusers[$forumid])) {
-                if ($subusers = forum_subscribed_users($courses[$courseid], $forums[$forumid], 0, false)) {
+                if ($subusers = forum_subscribed_users($courses[$courseid], $forums[$forumid], 0,
+                        get_context_instance(CONTEXT_MODULE, $coursemodules[$forumid]))) {
                     foreach ($subusers as $postuser) {
                         // do not try to mail users with stopped email
                         if ($postuser->emailstop) {
@@ -2464,10 +2471,28 @@ function forum_get_user_discussions($courseid, $userid, $groupid=0) {
 }
 
 /**
- * Returns list of user objects that are subscribed to this forum
+ * Get the list of potential subscribers to a forum. 
+ *
+ * @param object $forumcontext the forum context.
+ * @param integer $groupid the id of a group, or 0 for all groups.
+ * @param string $fields the list of fields to return for each user. As for get_users_by_capability.
+ * @param string $sort sort order. As for get_users_by_capability.
+ * @return array list of users.
  */
-function forum_subscribed_users($course, $forum, $groupid=0) {
+function forum_get_potential_subscribers($forumcontext, $groupid, $fields, $sort) {
+    return get_users_by_capability($forumcontext, 'mod/forum:initialsubscriptions', $fields, $sort, '', '', $groupid, '', false, true);
+}
 
+/**
+ * Returns list of user objects that are subscribed to this forum
+ *
+ * @param object $course the course
+ * @param forum $forum the forum
+ * @param integer $groupid group id, or 0 for all.
+ * @param object $context the forum context, to save re-fetching it where possible.
+ * @return array list of users.
+ */
+function forum_subscribed_users($course, $forum, $groupid=0, $context = NULL) {
     global $CFG;
 
     if ($groupid) {
@@ -2480,11 +2505,13 @@ function forum_subscribed_users($course, $forum, $groupid=0) {
     }
 
     if (forum_is_forcesubscribed($forum)) {
-        $context = get_context_instance(CONTEXT_COURSE, $course->id);
+        if (is_null($context)) {
+            $context = get_context_instance(CONTEXT_MODULE, get_coursemodule_from_instance('forum', $forum->id, $course->id));
+        }
         $sort = "u.email ASC";
         $fields ="u.id, u.username, u.firstname, u.lastname, u.maildisplay, u.mailformat, u.maildigest, u.emailstop, u.imagealt,
                   u.email, u.city, u.country, u.lastaccess, u.lastlogin, u.picture, u.timezone, u.theme, u.lang, u.trackforums, u.mnethostid";
-        $results = get_users_by_capability($context, 'mod/forum:initialsubscriptions', $fields, $sort, '','','','', false, true);
+        $results = forum_get_potential_subscribers($context, $groupid, $fields, $sort);
     } else {
         $results = get_records_sql("SELECT u.id, u.username, u.firstname, u.lastname, u.maildisplay, u.mailformat, u.maildigest, u.emailstop, u.imagealt,
                                    u.email, u.city, u.country, u.lastaccess, u.lastlogin, u.picture, u.timezone, u.theme, u.lang, u.trackforums, u.mnethostid
diff --git a/mod/forum/subscriber.html b/mod/forum/subscriber.html
index 15a920da23f..4074e915cfc 100644
--- a/mod/forum/subscriber.html
+++ b/mod/forum/subscriber.html
@@ -1,6 +1,5 @@
 
 <form id="subscriberform" method="post" action="subscribers.php">
-<input type="hidden" name="previoussearch" value="<?php p($previoussearch) ?>" />
 <input type="hidden" name="id" value="<?php echo $id?>" />
   <table align="center" border="0" cellpadding="5" cellspacing="0">
     <tr>
@@ -14,7 +13,7 @@
     </tr>
     <tr>
       <td valign="top">
-          <select name="removeselect[]" size="20" id="removeselect" multiple
+          <select name="removeselect[]" size="20" id="removeselect" multiple="multiple"
                   onFocus="getElementById('subscriberform').add.disabled=true;
                            getElementById('subscriberform').remove.disabled=false;
                            getElementById('subscriberform').addselect.selectedIndex=-1;">
@@ -34,12 +33,12 @@
         <br />
       </td>
       <td valign="top">
-          <select name="addselect[]" size="20" id="addselect" multiple
+          <select name="addselect[]" size="20" id="addselect" multiple="multiple"
                   onFocus="getElementById('subscriberform').add.disabled=false;
                            getElementById('subscriberform').remove.disabled=true;
                            getElementById('subscriberform').removeselect.selectedIndex=-1;">
           <?php
-              if (!empty($searchusers)) {
+              if (isset($searchusers)) {
                   echo "<optgroup label=\"$strsearchresults (" . count($searchusers) . ")\">\n";
                   foreach ($searchusers as $user) {
                       $fullname = fullname($user, true);
@@ -56,19 +55,10 @@
           ?>
          </select>
          <br />
-         <input type="text" name="searchtext" size="30" value="<?php p($searchtext, true) ?>" 
-                  onFocus ="getElementById('subscriberform').add.disabled=true;
-                            getElementById('subscriberform').remove.disabled=true;
-                            getElementById('subscriberform').removeselect.selectedIndex=-1;
-                            getElementById('subscriberform').addselect.selectedIndex=-1;"
-                  onkeydown = "var keyCode = event.which ? event.which : event.keyCode;
-                               if (keyCode == 13) {
-                                    getElementById('subscriberform').previoussearch.value=1;
-                                    getElementById('subscriberform').submit();
-                               } " />
+         <input type="text" name="searchtext" size="30" value="<?php p($searchtext, true) ?>" />
          <input name="search" id="search" type="submit" value="<?php p($strsearch) ?>" />
          <?php
-              if (!empty($searchusers)) {
+              if (isset($searchusers)) {
                   echo '<input name="showall" id="showall" type="submit" value="'.$strshowall.'" />'."\n";
               }
          ?>
diff --git a/mod/forum/subscribers.php b/mod/forum/subscribers.php
index 6e0fbf179b9..802a6fd4f02 100644
--- a/mod/forum/subscribers.php
+++ b/mod/forum/subscribers.php
@@ -34,7 +34,7 @@
     $strsubscribeall = get_string("subscribeall", "forum");
     $strsubscribenone = get_string("subscribenone", "forum");
     $strsubscribers = get_string("subscribers", "forum");
-    $strforums      = get_string("forums", "forum");
+    $strforums = get_string("forums", "forum");
 
     $navigation = build_navigation($strsubscribers, $cm);
 
@@ -56,7 +56,7 @@
 
     if (empty($USER->subscriptionsediting)) {         /// Display an overview of subscribers
 
-        if (! $users = forum_subscribed_users($course, $forum, $currentgroup) ) {
+        if (! $users = forum_subscribed_users($course, $forum, $currentgroup, $context) ) {
 
             print_heading(get_string("nosubscribers", "forum"));
 
@@ -93,12 +93,11 @@
     $strsubscribers = get_string("subscribers", "forum");
     $strforums      = get_string("forums", "forum");
 
+    $searchtext = optional_param('searchtext', '', PARAM_RAW);
     if ($frm = data_submitted()) {
 
 /// A form was submitted so process the input
-
         if (!empty($frm->add) and !empty($frm->addselect)) {
-
             foreach ($frm->addselect as $addsubscriber) {
                 if (! forum_subscribe($addsubscriber, $id)) {
                     error("Could not add subscriber with id $addsubscriber to this forum!");
@@ -111,48 +110,41 @@
                 }
             }
         } else if (!empty($frm->showall)) {
-            unset($frm->searchtext);
-            $frm->previoussearch = 0;
+            $searchtext = '';
         }
     }
 
-    $previoussearch = (!empty($frm->search) or (!empty($frm->previoussearch) && $frm->previoussearch == 1)) ;
-
 /// Get all existing subscribers for this forum.
-    if (!$subscribers = forum_subscribed_users($course, $forum, $currentgroup)) {
+    if (!$subscribers = forum_subscribed_users($course, $forum, $currentgroup, $context)) {
         $subscribers = array();
     }
 
-    $subscriberarray = array();
+/// Get all the potential subscribers excluding users already subscribed
+    $users = forum_get_potential_subscribers($context, $currentgroup, 'id,email,firstname,lastname', 'firstname ASC, lastname ASC');
+    if (!$users) {
+        $users = array();
+    }
     foreach ($subscribers as $subscriber) {
-        $subscriberarray[] = $subscriber->id;
-    }
-    $subscriberlist = implode(',', $subscriberarray);
-
-    unset($subscriberarray);
-
-/// Get search results excluding any users already subscribed
-
-    if (!empty($frm->searchtext) and $previoussearch) {
-        $searchusers = search_users($course->id, $currentgroup, $frm->searchtext, 'firstname ASC, lastname ASC', $subscriberlist);
+        unset($users[$subscriber->id]);
     }
 
-/// If no search results then get potential subscribers for this forum excluding users already subscribed
-    if (empty($searchusers)) {
-        if ($currentgroup) {
-            $users = get_group_users($currentgroup, 'firstname ASC, lastname ASC', $subscriberlist);
-        } else {
-             $users = get_course_users($course->id, 'firstname ASC, lastname ASC', $subscriberlist);
+/// This is yucky, but do the search in PHP, becuase the list we are using comes from get_users_by_capability,
+/// which does not allow searching in the database. Fortunately the list is only this list of users in this
+/// course, which is normally OK, except on the site course of a big site. But before you can enter a search
+/// term, you have already seen a page that lists everyone, since this code never does paging, so you have probably
+/// already crashed your server if you are going to. This will be fixed properly for Moodle 2.0: MDL-17550.
+    if ($searchtext) {
+        $searchusers = array();
+        $lcsearchtext = moodle_strtolower($searchtext);
+        foreach ($users as $userid => $user) {
+            if (strpos(moodle_strtolower($user->email), $lcsearchtext) !== false ||
+                    strpos(moodle_strtolower($user->firstname . ' ' . $user->lastname), $lcsearchtext) !== false) {
+                $searchusers[$userid] = $user;
+            }
+            unset($users[$userid]);
         }
-        if (!$users) {
-            $users = array();
-        }
-
     }
 
-    $searchtext = (isset($frm->searchtext)) ? $frm->searchtext : "";
-    $previoussearch = ($previoussearch) ? '1' : '0';
-
     print_simple_box_start('center');
 
     include('subscriber.html');