At the IETF, I officially work on authoring and instant messaging protocols. I've also been getting interested in some of the more general notification (including instant messaging and presence notification) architecture challenges. Instant messaging and presence are so useful in themselves that people are willing to have an account on a buddy list server, start a separate client and hold open a connection to the server. However, there are many other kinds of notifications users might be interested in getting on their computer or on various devices, and it's not going to be feasible to do them all with new client software, new protocols, new servers and services, and still be managable.
I have finally documented some of the notification architecture issues in a requirements draft for server-to-server notification aggregation.