That VoIP business is getting a tough one, as shown by such actions as the recent "Skype China plot". It is becoming incredibly difficult to differentiate by saying "save money with cheap calls". Now Jahjah (Israeli company with headquarters in Mountain View, CA) is trying a new marketing coup by offering FREE calls between phones. How does that work? If you and your to-be-called party are both registered with Jahjah, then calls are for free in the Zone 1 and Zone 2 areas.

The new thing now is that calls are set up between your phones and not your PCs, since most users prefer to talk through their phones. So you can do a call from your cell phone to someome else's cell phone or landline phone. They also have some plugins/support for Outlook, Firefox, Mac address book and Plaxo.

The business model/strategy is obviously to get a critical mass of subscribers quickly and then make money with premium services and probably with ads. If this does not happen fast enough they will use up their money and shut down (or sell) I assume.
Truly entrepreneurial, I must say. I assume if you still want to succeed in the VoIP space you have to do such things. That alone deserves respect I think for Jahjah! Good luck, guys. We will try it now too.