I realized I want more when, a while back, I saw someone working on a social network over email. I realized that it's a brilliantly low-tech solution to a problem people are trying to solve in fairly complex and inventive ways (like Scuttlebutt). Social network posts as email would be an interesting approach to the problem.
Back to my original statement, data emails would allow users to carry a pile of application data (like their social net feed) with them. Since email is something federated, backup-able, migrate-able, etc - users would own their own data. I like that idea.
Fundamentally I love the idea of email. I do of course have reservations with the idea of introducing non-human oriented emails, but I hope you (reader) can look past that and onto the intent - offering slightly more feature to a robust, tried and true platform.
I say "slightly more" with care. Lest we make email a steaming pile of innovation like we always do.
The current trend is actually the reverse: general communication is being replaced by specific communication that is better suited for the type of communication it is. Social, pictures, group chat, business collaboration, negotiation/agreement, etc - email CAN function as the medium but is not ideal, whereas the apps that replace email streamline the communication experience.