Hal,
Apples and oranges. Vonage uses the internet, a cable modem only uses the cable lines for VoIP
But in many cases the internet is provided by the cable company. In my area the cable is run out from the main office in fiber and connected to coax in the neighborhoods. Loss of power for the media converter results in loss of cable service and internet service. We have many areas of town where the only broadband choice is the cable as the homes are over 15,000 wire feet from the central office and won't support DSL.
Don
