Found this comment on sound and interaction design by Hans Samuelson on the Ivrea Hub, which helped me understand in part why my Skype cold-calling experience made me have such a knee-jerk reaction:
“the public nature of sound – it projects and radiates, it is an active expression against which there is little defense. Its essentially impossible to shut your ears; eyelids are a last line of defense against visual noise, but there is no equivalent for touch, or even sound. The always-on world ”
Petafloptimism 
Text vs. Audio Messaging
Blackbelt Jones on the potential differences between email or IM spam and audio conferencing spam possible with new p2p audio technologies like Skype: I think I just got telemarketed over Skype.Someone I don’t know from Sweden called me and said…