This patch allows disabling the backlinks in the config file by setting nobacklinks to 0. It is backwards compatible, and by default enables backlinks in the generated pages.
--- IkiWiki/Render.pm.orig2	2009-01-06 14:54:01.000000000 +1300
+++ IkiWiki/Render.pm	2009-01-06 14:55:08.000000000 +1300
@@ -107,7 +107,8 @@
 		$template->param(have_actions => 1);
 	}
 
-	my @backlinks=sort { $a->{page} cmp $b->{page} } backlinks($page);
+	my @backlinks=sort { $a->{page} cmp $b->{page} } backlinks($page)
+		unless defined $config{nobacklinks} && $config{nobacklinks} == 0;
 	my ($backlinks, $more_backlinks);
 	if (@backlinks <= $config{numbacklinks} || ! $config{numbacklinks}) {
 		$backlinks=\@backlinks;