They are not called on each page!
Check the misc.php (because this page is calling the buddylist popup)
PHP Code:
$buddys = $db->query_read_slave("
SELECT
user.username, (user.options & " . $vbulletin->bf_misc_useroptions['invisible'] . ") AS invisible, user.userid, session.lastactivity
FROM " . TABLE_PREFIX . "userlist AS userlist
LEFT JOIN " . TABLE_PREFIX . "user AS user ON(user.userid = userlist.relationid)
LEFT JOIN " . TABLE_PREFIX . "session AS session ON(session.userid = user.userid)
WHERE userlist.userid = {$vbulletin->userinfo['userid']} AND userlist.relationid = user.userid AND type = 'buddy'
ORDER BY username ASC, session.lastactivity DESC
");