I think someone who has equipment engaged in DDoS attacks might be a bigger cost to the telecom than they are paying anyway. Those 20,000 customers are either using disproportionately more bandwidth and resources or they are at least unwittingly involved in illegal activity, so Comcast would have either a financial incentive or social obligation to temporarily suspend their service. The company should be complaining to the customer, and they should be worried about losing their service. If every competitive provider had these very narrow standards, customers should be more worried about not having Internet because of their security illiteracy.