well, it was looking like an email client (sender[s]/recipient[s] + message thread), but was "realtime", so it's not difficult to see it as an instant messenger

well, it was looking like an email client (sender[s]/recipient[s] + message thread), but was "realtime", so it's not difficult to see it as an instant messenger (the parent message wasn't referring to a chat box inside Wave). But then again, it's not difficult to see any social network as a glorified forum if you look hard enough