There is a very strong control over telephony in many countries. Many counties intend to make this control more and more stronger. In the Russia, when I live, for example the Putin's and Medvedev's bloody dictatorial regim now intend to ban VoIP telephony: http://www.point.ru/news/stories/20598/ Besides, there is no effective open source system of VoIP telepony which let people freely talk and connect by chat and sending-receiving files between each other without any control from Governments, companies etc., maintaining anonimity and encryption of communication at the same time. We have only the skype but it is propietary soft belonging to a private company aiming only gain profit not maintaining anonimity and independence people's contacting from Governments etc. As knows this company lets the Chineese authorities to know about conversations between Chineese. So they can provide confidential information about users any other Government. But I think that their protocol is very intresting becouse the skype network building on a peer-to-peer model, that user directory will be entirelyentralized and distributed among the nodes in the network, and use encrypted connection insluding connetion with the exit node when making calls to ordinary telephone. Maybe I am not quite right, but this network system seems to me looking like the Tor network. I think that building such system based on open sources, maintaining by open source community will protect anonymity and privacy of people and independence each of us from goverments, corporations etc. control, becouse we will be able to call each other without any state or corporate control over our telephone calls.
I think that it will be very good to include in the Tor project creatings and maintaining such VoIP telephone system or doing this as an independent project concurrently of the To r project. Or including in the Tor project simply maintaining UDP -connections that may let using SIP and etc. protocols through the Tor.