Implements hook_menu_link_load().
function user_menu_link_load($menu_links) {
// Hide the "User account" link for anonymous users.
foreach ($menu_links as $link) {
if ($link['link_path'] == 'user' && $link['module'] == 'system' && !$GLOBALS['user']->uid) {
$link['hidden'] = 1;
}
}
}