I installed iTunes 5.0 and when I was done my firewall asked me if I wanted some service called Bonjour to access the internet. It would seem iTunes 5.0 installs this program without asking.
Thought I should let everyone know. Research it for yourself, but anything that is installed without my permission and then attempts to subtlely access the interweb is not a good thing
EDIT: Okay, it's not entirely without asking, as it does appear in the "About iTunes" section (one of those multi page things that most people typically skip during install) when you install, but I still don't like the existence of this program on my computer, especially given the inability to uninstall it