Perhaps we are forgetting that Amazon is a victim as well. If Amazon is unable to seek punishment against malicious users of its site, it is forced to spend its time and money patching security holes and preventing future attacks, in addition to repairing lost good will from customers and authors.
It always surprises me how quick people are to jump to the conclusion that the website operator is at fault for these sorts of malicious uses. It flies in the face of simple economics. The burden on Amazon to protect its site probably ranges in the thousands or millions of dollars; the benefit to the malicious user is a couple of laughs and a funny blog post. It would seem economically inefficient to say that the burden lies on Amazon, in this situation, to protect itself.
(Indeed, I don't believe anyone would analogously say that a thief is not responsible for acts of theft, because they provide a "free lesson in home security" to the victim. Why the difference when we move to the online realm?)