If a court finds out they did indeed obtain the list illegally, and they raise prices to offset this, then you'll have to switch companies if you don't want to pay for your provider's loss.
It's actually Vonages' fault here, not SR. They shouldn't have stolen the list for free advertising.
If they paid the liquidator then they didn't purchase it illegally. The liquidator may not have been allowed to sell it but that's not Vonage's issue. As I see it makes sense to do what Vonage did. First they tried to purchase the list from Sunrocket and they said no. Then, once the company went belly up they tried to buy it from the liquidator (who then had responsibility for all of the SunRocket assets) and they said yes. That's just normal business practices when a company goes out of business. At worst Vonage will have to give the data back to Sunrocket.