No more sharing playlist and music in the iTunes network unless you are on a local network. Apple fixed the feature that was being exploited by users. I am sure this will cause the hackers out there to get pissed and make a exploit.
Apple made this comment to CNet “The new iTunes 4.0.1 update limits Rendezvous music sharing to work only between computers on a local network (its intended use) and disables music sharing over the Internet.” [CNet]