There are similar existing web calling provider such as Skype, and Genesis, but none are comparable in size, and depth of service that is provided by Google Voice.

In the information Age, International Corporations no longer flies its executive around the world for meetings, rather Video and Call Conference is a popular alternative.

Google provides free Call Conferencing (in specific countries for now, but Google intends to go worldwide), which would surely take over businesses for many existing service providers (ex. Premiere Global) who charge high rates for private conference lines.