I'm researching some historic material that has Skype relevance. I found RFC 741 from 22 Nov 1977 (almost 30 years ago!) particularly telling. It talks about Network Voice Protocol, one of the original protocols/purposes of ARPAnet. NVP never took off, but the goal of using packet-switched communication networks for voice exchange remained. Does this have some similarity to what Skype is doing? :)
The major objective of ARPA's Network Secure Communications (NSC) project is to develop and demonstrate the feasibility of secure, high-quality, low-bandwidth, real-time, full-duplex (two-way) digital voice communications over packet-switched computer communications networks.