If it's determined that a Comcast is doing this, the resulting bad word of mouth could literally
destroy them as a company. Providing IP service is the only business that matters. In 10 years cable TV may be dead

as everyone will be able to broadcast over IP. No more channels, buy your basketball from Google to play on your video ipod connected to your home monitor.
And market perception is the biggest differentiator. The only differentiator. Anyone can move bits; depending where you're sitting, you may be bombarded with them. You can get broadband wi-fi at your local coffee place, for example.
Cisco has far more sway than any two-bit network-sniffing company and could well treat such packet warfare as network errors in the future, and try to route around them automatically. Remember the axiom, "the Internet treats censorship as network failure and routes around it." Voice is about 64k of bandwidth at the most, trivial to route around. That's why Vonage has a market to begin with.
New phones will even be wi-fi enabled, so if your own bandwidth doesn't match the bandwidth you get at work, or at McDonalds, providers will get complaint after complaint until they get it "fixed" and inferior service will clearly be the road to failure. Even management will understand because of how quickly it will effect their bottom lines.
We are in charge.