That’s a shame, since it means that the
aim: links that are scattered around the Web won’t work with iChat. A bit of poking around does reveal that iChat responds to the
iChat: URL scheme, but I couldn’t make it do anything useful for Web links;
iChat:compose?card=«uid» will open a chat with the person with UID «uid» in your Mac OS X address book, but that’s Not Helpful.
I did figure out how to crash iChat from the Web browser, though. Whee.