I completely agree that the customers in these cases should be held responsible for the services they purchased from their ISPs.
Let's all try to keep in mind that the two customers mentioned in the article as being on the receiving end of large bills were businesses, not consumers.
In the course of running his "small high-tech company," Mr. Liber could have hired a part-time IT guy to watch over his systems and keep them patched and healthy. Doing so could have cost him less than the $85,000 his ISP billed him for. He also could have procured liability insurance for his business. Perhaps he also could have bought a firewall, or a better one.
Any of these options would have cost Mr. Liber's business some money. He appears to have chosen instead to accept higher business risk in exchange for a higher potential profit margin. And, when the bills arrived, he could have chosen to pay them. Instead, he chose to file for bankruptcy. Each step of the way, he had options, and he made his choices as he saw fit.
Was this truly negligence, or a calculated business risk?