The thing is, email is already distributed. SMTP, NNTP, ftp, talk, finger, etc., we already have all these decentralized applications and protocols. But the adoption of dynamic IP allocation and firewalls has made it quite inconvenient to run these services. Now there's a whole other layer built to deal with these issues, and so there could very well be a pendulum swing in the direction of decentralization all over again.

My feeling is that if we could reclaim all those good old protocols (ftp, and all the other above-mentioned ones) and if we could run them locally easily and added a couple more generic services such as bittorrent and gnutella (for search), we'd have a nice decentralized stack to build new applications on.