Residential users continue to adopt VoIP at a rapid rate, with more than 9 million households using the service at the end of the second quarter, according to a new report from In-Stat.

Subscribers using facilities-based VoIP have created a horse race between Vonage and Time Warner Cable users, with Vonage reporting 1.7 million users to Time Warner's 1.6 million. In-Stat says Skype dominates software-based VoIP with 2.1 million active U.S. households using the eBay service.

Charles Gerlach, In-Stat's director of consulting, issued the report this week, suggesting that VoIP services are having an impact on traditional landline and cell phone service providers.

The market research firm said that nearly half of VoIP residential subscribers discontinued their conventional phone service when they signed up for Internet phoning.

Microsoft made a strong showing in the quarter in the software-based segment, recording 1.1 million subscribers. Yahoo Messenger with Voice had 1 million subscribers and Google Talk, 658,000, according to In-Stat.