The efficiency of communicating in a way that allows your team to build concrete document artifacts as a direct consequence of that communication, comprises a lower-energy state for workers into which they must fall.
In Wave, the idiom of interleaved communication threads becomes a "first class" structure, capturing both my ownership of a reply and its relative sequence in the discussion. Unlike email and forums where one sees sausage stuffing of the replied-to bodies with every reply, Wave repetition is minimized except to replicate information to clients. Governments and institutions with requirements for auditing and security will, I think, look at this as a good thing because it will allow conversations to be traced much more rigorously; I would bet it won't be long before customary governance rules require something like Wave and deprecates email services. That is, I suspect this will wipe out email, news, and I.M, both legally and technically.