Any VoIP company that is trying to be a voice replacement, is living on borrowed time (and money.) Folks over at My VoIP Provider did a historical study from August 2005 through October 2006, and found that 85 VoIP providers were kicked to the curb.
This is global data, but the issues facing these companies are pretty much the same… how to stay in business when all you can do is fight on price, and have no distinguishing features! Even AOL had to shutter its Total Talk. Vonage is no where close to being profitable, and Skype has to give away its money making services (in North America) to get some traction. And the incumbents are flexing their muscle, and taking market share by the month.