Interesting point, although I don't consider email a platform like I do Facebook or Twitter. While there's no central database, there's a means of determining w

Interesting point, although I don't consider email a platform like I do Facebook or Twitter. While there's no central database, there's a means of determining where the right server to talk to lives attached to the username. We'd need some sort of DNS-for-handles in order to implement something similar for a new protocol, unless you want your handle tied to a domain (in which case you've just remade email with a RESTful API and a length limit)