Nicknames in Jabber
Inspired by a post by cbas, I have thought of a new application for Publish Subscribe. Legacy IM systems like MSN have a feature to show a piece of text as someone's nickname. Since you define the name of people on your roster yourself, some client may like to implement changing nicknames as well. I think pub/sub is nice for this: people who want your strange changing nicks can be notified of such a change.