Then all the DMCA problems would be immediately gone. It's sad that the gittorrent idea never really took off.
E-mail is the golden example on how not to solve this. It's unsecure, unvalidateable, unverifiable, exploitable and everything in between can block it or listen to it. And it uses another, unencrypted, transport protocol, which means it is not related to git at all.
The reason why GitHub exploded is the UX experience and the convenience that comes with it. But on the technical side there is no reason not to integrate those features into git itself (or git-web for that matter).