I was thinking the exact same thing. It could very well be a good idea that is ahead of it's time. We are still wedded tightly to traditional email, but something like Wave could very well take over in the next say, decade or so.
EDIT: Jive are one example, not the link I had in mind though:
http://techcrunch.com/2010/07/20/readying-for-an-ipo-jive-so...