Don't know if anyone is aware of this yet but it's already happening.
http://www.nytimes.com/2008/10/25/technology/internet/25phone.html?_r=1&ref=technology&oref=slogin
http://www.nytimes.com/2008/10/25/technology/internet/25phone.html?_r=1&ref=technology&oref=slogin