I don’t think that Google Wave will ever replace the “communication” tools, so you won’t be able to unload IM / Skype / email (and the imho Google wave ping function seems to suck).
For this, it is important to jointly and simultaneously edit content in a chaotic initial phase, whether it be documentation, emails, press releases or anything else. Then, when the documents are stable, it makes it easier for me to manage them as Google documents, which can still be versions, but in a more mature environment.
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