I recently read on Quora that reinventing email or making email a thing of the past is among the startup ideas that persistently fail. "The first truly social

I recently read on Quora that reinventing email or making email a thing of the past is among the startup ideas that persistently fail. "The first truly social email service." Is email something social? I'm not sure of that. And here we don't even know what the service is. Will I get an email address? Will it be compatible with the normal email? Is it another Facebook Message? I don't see why people would request an invite and give post.fm their email address if they don't know what to expect.