Just to let you all know that if you want to use Matt's Auto Links Discovery Plugin for wpmu all you gotta do is tweak it a very small tad.
1. Download it from here:
http://mattread.com/projects/wp-plugins/auto-links-discovery-plugin/
2. Edit the plugin... find the line:
var autoLinksFile = '<?php echo $site_url ?>/wp-content/plugins/auto-links.php';
3. Change /plugins/ to /mu-plugins/ (duh!!!)
4. Drop it in place
Voila! Magic... great for the users that are lazy and rather email you to do it!!
