I'd posit that the reason everything gets jammmed through HTTP/HTTPS/SMTP/POP/IMAP/DNS now is that those are the only things we can reliably get through every f

I'd posit that the reason everything gets jammmed through HTTP/HTTPS/SMTP/POP/IMAP/DNS now is that those are the only things we can reliably get through every firewall. Home firewalls are easy. Most already have UPNP or NAT-PMP enabled, so the app can easily poke holes--even in TCP! Corporate ones (people procrastinating at work is a fat chunk of internet traffic) will have all kinds of ad-hoc rules that struck the network guy's fancy at the time. For a truly P2P net (grandma-to-grandma), one side isn't enough.