Jo Walsh talks about conversation.
I think there's a thread of something there; damned if I know what it is. I kind of picture something like our trac + subversion setup.
You have a conversation with whomever, and you just use a WikiWord to tag it. Software behind the scenes automagically traces the when, who, and what: it shouldn't be hard to write plugins / specific filters to pore over log files / etc.
It also just so happens I got back to playing with cocomment.com - it's ALMOST a solution for Jo's blogging conversations.