Honestly, though, it completely surprises me that the various IM clients haven't learned how to play nice with each other and settled on an interoperability standard. We should have had all these capabilities a long long time ago.

There is an IETF working group, Instant Messaging and Presence Protocol, that is working on this, but they're taking way too long about it. The folks at Jabber have a nice solution, except for the fact that, at least as of the last time I looked, all their clients sucked. The server is really nice, though. There's also a group called IMUnified, which, apparently, is a group of IM companies ganging up on AOL (I infer this based on the fact that AOL is not in the group, and that they seem to refuse to include the Jabber folks).

But you're right. This should have been solved long ago. Too bad that IM didn't become popular before the mass commercialization of the Internet. It probably would have taken less than a year for massive interoperability to occur.