Well, the court has ruled Vonage in violation of Verizon's patenets, so I guess that decision has been made. Further, a court has issued an injunction against vonage continuing to use the infringing technology.
My understanding is that Verizon's patents cover the besic technology by which any VOIP service connects to the POTS system, as defined in published standards for this. So if Vonage gets hit others will get hit.
A bit more info:
http://en.wikipedia.org/wiki/Vonage#Verizon_lawsuit
My home phone's on Vonage. I'm actually more concerned about losing the number (going on 20 years with this number).