VOIP–a Tower of Babel?

My spin: FYI
News Clip: Jeff Pulver is the top cheerleader for voice over Internet Protocol, a cheaper form of telephoning that’s winning a few thousand converts every week.
He should be happy. But instead he thinks he’s helped create a Tower of Babel.
Pulver’s new venture, Free World Dial-Up, is among a new class of providers of voice over Internet Protocol (VOIP) that sell or give away Internet telephone calling plans. While the services can differ dramatically in price or quality, one thing is constant: Many subscribers of different VOIP services can’t talk to each other.
(full story)