AOL

Currently there is no functional voice communications backplane on the web. Google tried with GoogleTalk but the lack of service interworking with the regular telephone network and the existing limitations of libjingle limit the usefulness of recombined voice service applications based on GoogleTalk beta.

Yahoo! has just launched Yahoo! Messenger with Voice 7.0 with broader support for PC to phone calling. This service offers even cheaper per minute rates than SkypeOut as noted by Stuart Henshall of Skype Journal. With extensive network cores, Yahoo!, Google, and other leading web portals are in pretty good positions to establish themselves as competing communications backplanes. I would suspect that over time, Yahoo, Google / AOL, Microsoft Live, and possibly ...Skype will all offer varying capabilities of a communications 2.0 backplane.