Phone Calling Over Internet Is Attracting More Interest "Internet calling currently accounts for more than 10 percent of international calling traffic, with about 18 billion minutes worldwide, up from 9.9 billion minutes at the end of 2001, according to the research firm Telegeography."
I think the author missed a key dimension -- the use of PC-based tools such as Windows Messenger and Macromedia Flash Communication Server-based apps; such tools facilitate long-distance audio and video (although in the case of Windows Messenger there are still lots of firewall and NAT etc. challenges).