Vonage is learning this the hard way. Many companies go through product development or launch of new services without good understanding or execution of their IP strategy and then in some cases like Vonage’s pay a huge price that can literally drive you out of business.
Vonage paid Sprint $80M and is likely to pay a similar amount to settle with Verizon and believe me there are others with VoIP patents as well. A licensing arrangement up front would have set them back by only a fraction.