As someone who used to work for an independent VoIP provider, I am not surprised to see SunRocket join the deadpool. There's a great post by Om Malik on his site.
After all, the costs of acquisition are so high. Consider:
1) the cost of advertising,
2) the cost of the telephone adaptor box that in most cases is given to the customer free of charge as an inticement to signup,
3) the cost of provisioning the calls....they just don't come out of thin air,
4) the cost of providing Customer Support....24/7,
5) and on, and on.
It's has been rumored that Vonage's cost of acquisition (COA) is somewhere north of $250 per customer. Do the math, spend $250 to acquire a customer, give them the first month free, a free adaptor box and free Customer Support. How in the heck can anyone make money at this???
Granted Vonage spends a TON on advertising--way more than SunRocket did.
But the, SunRocket was also giving away a free cordless phone with a signup.

It's like the old saying "we lose money on every sale, but we'll make it up in the volume".
Personally, I think, VoIP should be left in the hands of the cable companies and phone companies. They have the financial backing and in most cases, don't have to chase new customers the way VoIP companies do.