The number of U.S. subscribers to Internet telephony (VoIP) services leapt to 2.7 million subscribers in the second quarter of 2005, up from 444,000 a year ago, according to a report from market research firm TeleGeography. While revenue from U.S. VoIP for the quarter was $220 million, the firm expects that nascent offerings from cable TV providers will cause that figure to soar to $3 billion by 2007. Currently, the largest U.S. provider is Vonage, with an estimated 750,000 subscribers, followed by the Internet telephone service offered by Time Warner Cable.