Back when independent ISPs tried to fend off AOL, the same kind of thing happened. The ISPs tried to sell network uptime, connection quality, and modem speeds. AOL understood it was selling a low-margin commodity and countered with: "Try this! It's fun." Oh, and they carpet-bombed everyone with free disks. Long story short: AOL won.
With VOIP, the incumbent carriers, the guardians of the PSTN, are figuring out the game. Consider this observation from a source at a big, reputable phone company, that is just beginning to roll out VOIP services in its territory:
We recently did a survey of customers in one of our major metro areas who have switched to a VOIP provider. Nearly 3 out of 4 of those customers said they have never heard of VOIP... and they're VOIP subscribers!
What a world...
— Phil Harvey, News Editor, Light Reading