I certainly wouldn't be comfortable with my peers having the opportunity to control my email and the myriad of accounts associated with it. I can't imagine they would be happy with me doing the same with their data.
> We also show how to configure encryption in their mail clients
Encryption is fairly useless without authentication, and we can safely assume that the NSA has control of Certificate Authorities.
> Think about it. There are enough tech geeks. Every geek should need to know how to do this anyhow. This will scale.
I've been battling with the concept of hosting my email for quite some time, and it always boils down to being a horrific thing to set up. There's a pile of easy ways you can screw up and make something insecure or spam-ridden. I spent a good day trying to put together a solution I was happy with, but couldn't.