Check out this story about Canada's Shaw Cable being sued by ZingoTel for not allowing the ZingoTel ads to run on the cable network.
Interesting. As a case in point when AT&T rolled out CallVantage in the USA they made a very concerted effort to make the cable operators their friends.
To me, blocking the running of an ad, for anything short of violating what is called Standards and Practice is silly. If Shaw has a better product people will buy it. If Zingo (or Vonage) or anyone else wants to pay for ads then don't let envy or greed be the deciding factor. Besides, if the courts side with the complaintants Shaw will likely end up having to insure they don't enforce their QoS rules on ZingoTel customers and pay out in both cash and adverts as part of the damages. To me that would be the way to settle it. Not a lot of cash, just commercials.