Email has been scaling just fine for years. And I've run some reasonably successful open source projects (including SpamAssassin at the height of its success).

Email has been scaling just fine for years. And I've run some reasonably successful open source projects (including SpamAssassin at the height of its success). I really don't see the problem. The fact that an email is easy to send without knowing the recipient is a huge benefit of email. No other electronic communication system offers this benefit (and unfortunately it enables spam, but that's an entirely different discussion).