> And don't give me some crap about firewalls, because email and IRC and games work perfectly even among the technically uninformed majority.
No, they don't. Most ISPs filter block 25 in both directions, and many block IRC since it's used for botnet coordination. Have you tried it (on an ISP that is commonly used by the technically uninformed majority)?
Tunnelling over HTTP or better yet HTTPS is becoming quite common because it's the only thing guaranteed to work. "... for various reasons, different application layer protocols are increasingly being carried over TLS using a small set of TCP port numbers, most often port 443."
It's also generally the case that few people play large-bandwidth games on public networks at e.g. cafes, whereas a social networking protocol is useful if it's accessible from those sorts of restricted environments. In particular, a cryptographically-interesting social networking protocol is also quite useful from repressive countries with incompetent national ISPs.